diff --git a/play.ipynb b/play.ipynb
new file mode 100644
index 0000000..f4f87ec
--- /dev/null
+++ b/play.ipynb
@@ -0,0 +1,878 @@
+{
+ "metadata": {
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.9.6"
+  },
+  "orig_nbformat": 4,
+  "kernelspec": {
+   "name": "python3",
+   "display_name": "Python 3.9.6 64-bit ('xp-env': conda)"
+  },
+  "interpreter": {
+   "hash": "652fa5bafa2b8576ce7064e959b44480f5f8a15c86e6a8f20ca39abe1301c9a8"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2,
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "error",
+     "ename": "AttributeError",
+     "evalue": "`SummaryEstimator.key` has not yet been assigned a value.",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-2-5250fdbcb543>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmodel_specs\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mSummaryEstimator\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/__init__.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0msnapy\u001b[0m  \u001b[0;31m# noqa: F401; Import snapy before kragle to use snapy magics\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 6\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mbuilder\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mBuilder\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      7\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mhelpers\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mbuild_library\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      8\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpaths\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mBUILDERS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mMETRICS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mREPORTS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mSOURCES_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mQUERIES_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mFILTERS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mDIMENSIONS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mREPORT_CONFIGURATIONS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mCONFIG_SOURCES_DIR\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/__init__.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;34m\"\"\"Utility functions.\"\"\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0madd_on\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAddOn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0mafter_steps\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAfterExecutionStep\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0manalysis_context\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAnalysisContext\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0mconfig\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mCONFIG\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/add_on.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      6\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdimension\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mDimension\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 7\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmetric\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mMetric\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      8\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0merrors\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mValidationError\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/metric.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m     38\u001b[0m     \u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m'options'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     39\u001b[0m )\n\u001b[0;32m---> 40\u001b[0;31m \u001b[0;32mclass\u001b[0m \u001b[0mMetric\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mmetaclass\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mSubclassRegisteringMeta\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     41\u001b[0m     \"\"\"\n\u001b[1;32m     42\u001b[0m     \u001b[0mDefines\u001b[0m \u001b[0ma\u001b[0m \u001b[0mmetric\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/metric.py\u001b[0m in \u001b[0;36mMetric\u001b[0;34m()\u001b[0m\n\u001b[1;32m    187\u001b[0m     \u001b[0mcompression_overrides\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mDict\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mstr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mTerm\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m{\u001b[0m\u001b[0;34m}\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    188\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 189\u001b[0;31m     \u001b[0mmodels\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mList\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mModel\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m[\u001b[0m\u001b[0mDescriptiveStats\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mTTestStats\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    190\u001b[0m     \u001b[0mp_value_threshold\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mfloat\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;36m0.05\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    191\u001b[0m     \u001b[0mearly_stopping_alpha\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mOptional\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mfloat\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, key, data, engine, measure, link, hyperparams, estimations, label, visualizations, layout, compression_requirements, get_cell_significance, summary_estimators, treatment_effect_estimators, treatment_family_estimators, segment_by_covariates, summary_statistics, treatment_effect_statistics)\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36minit\u001b[0;34m(spec_cls, self, **kwargs)\u001b[0m\n\u001b[1;32m     85\u001b[0m                 \u001b[0;32mif\u001b[0m \u001b[0mcopy_required\u001b[0m \u001b[0;32mand\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0misinstance\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0mint\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mstr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtuple\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     86\u001b[0m                     \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mcopy\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdeepcopy\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 87\u001b[0;31m                 \u001b[0msetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     88\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     89\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0minstance_metadata\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__setattr__\u001b[0;34m(self, attr, value, force)\u001b[0m\n\u001b[1;32m    162\u001b[0m             \u001b[0mattr_spec\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__spec_class__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mattrs\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mget\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    163\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 164\u001b[0;31m                 \u001b[0mWithAttrMethod\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0m_inplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    165\u001b[0m                 \u001b[0;32mreturn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    166\u001b[0m             \u001b[0mmutate_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0minplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtype_check\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mforce\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mforce\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/scalar.py\u001b[0m in \u001b[0;36mwith_attr\u001b[0;34m(attr_spec, self, _new_value, _inplace, _if, **attrs)\u001b[0m\n\u001b[1;32m     29\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     30\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mis_collection\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 31\u001b[0;31m             _new_value = attr_spec.collection_mutator_type(\n\u001b[0m\u001b[1;32m     32\u001b[0m                 \u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtype\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mcollection\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0m_new_value\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mname\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     33\u001b[0m             ).prepare(item_preparer=functools.partial(attr_spec.prepare_item, self)).collection\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36mprepare\u001b[0;34m(self, item_preparer)\u001b[0m\n\u001b[1;32m     33\u001b[0m             \u001b[0mitems\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     34\u001b[0m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_create_collection\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 35\u001b[0;31m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0madd_items\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitems\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mitem_preparer\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     36\u001b[0m             \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     37\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;32mor\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mitem_preparer\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36madd_items\u001b[0;34m(self, items, preparer)\u001b[0m\n\u001b[1;32m     79\u001b[0m         \u001b[0mpreparer\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mpreparer\u001b[0m \u001b[0;32mor\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0;32mlambda\u001b[0m \u001b[0mitem\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     80\u001b[0m         \u001b[0;32mfor\u001b[0m \u001b[0mitem\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mitems\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 81\u001b[0;31m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0madd_item\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mpreparer\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     82\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     83\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36madd_item\u001b[0;34m(self, item, replace, attrs)\u001b[0m\n\u001b[1;32m     67\u001b[0m         ):\n\u001b[1;32m     68\u001b[0m             \u001b[0mitem\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mitem_spec_type\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 69\u001b[0;31m         return self._mutate_collection(\n\u001b[0m\u001b[1;32m     70\u001b[0m             \u001b[0mvalue_or_index\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     71\u001b[0m             \u001b[0mextractor\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_extractor\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/base.py\u001b[0m in \u001b[0;36m_mutate_collection\u001b[0;34m(self, value_or_index, extractor, inserter, require_pre_existent, new_item, transform, attrs, attr_transforms, replace, inplace)\u001b[0m\n\u001b[1;32m     73\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0mMISSING\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     74\u001b[0m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_create_collection\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 75\u001b[0;31m         index, old_item = extractor(\n\u001b[0m\u001b[1;32m     76\u001b[0m             \u001b[0mvalue_or_index\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mraise_if_missing\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mrequire_pre_existent\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     77\u001b[0m         )\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36m_extractor\u001b[0;34m(self, value_or_index, raise_if_missing)\u001b[0m\n\u001b[1;32m     15\u001b[0m         return (\n\u001b[1;32m     16\u001b[0m             \u001b[0mvalue_or_index\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 17\u001b[0;31m             \u001b[0mvalue_or_index\u001b[0m \u001b[0;32mif\u001b[0m \u001b[0mvalue_or_index\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;32melse\u001b[0m \u001b[0mMISSING\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     18\u001b[0m         )\n\u001b[1;32m     19\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/types/keyed.py\u001b[0m in \u001b[0;36m__contains__\u001b[0;34m(self, item_or_key)\u001b[0m\n\u001b[1;32m    274\u001b[0m         \u001b[0;31m# Check whether item_or_key exists as a value\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    275\u001b[0m         \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 276\u001b[0;31m             \u001b[0mkey\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mkey\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem_or_key\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    277\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mkey\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_dict\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    278\u001b[0m                 return (\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/types/keyed.py\u001b[0m in \u001b[0;36m__get_item_key\u001b[0;34m(self, item)\u001b[0m\n\u001b[1;32m     39\u001b[0m             \u001b[0mkey\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mitem\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__spec_class__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mkey\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     40\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mkey\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 41\u001b[0;31m                 \u001b[0;32mreturn\u001b[0m \u001b[0mgetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mkey\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     42\u001b[0m         \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     43\u001b[0m             \u001b[0mhash\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__getattr__\u001b[0;34m(self, attr)\u001b[0m\n\u001b[1;32m    138\u001b[0m                 \u001b[0;32mand\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0minspect\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0misdatadescriptor\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mgetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__class__\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    139\u001b[0m             ):\n\u001b[0;32m--> 140\u001b[0;31m                 raise AttributeError(\n\u001b[0m\u001b[1;32m    141\u001b[0m                     \u001b[0;34mf\"`{self.__class__.__name__}.{attr}` has not yet been assigned a value.\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    142\u001b[0m                 )\n",
+      "\u001b[0;31mAttributeError\u001b[0m: `SummaryEstimator.key` has not yet been assigned a value."
+     ]
+    }
+   ],
+   "source": [
+    "from metrics_repo.model_specs import SummaryEstimator"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from spec_classes import spec_class"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "@spec_class(key='key')\n",
+    "class MySpec:\n",
+    "    key: str"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "execute_result",
+     "data": {
+      "text/plain": [
+       "MySpec(key='asd')"
+      ]
+     },
+     "metadata": {},
+     "execution_count": 6
+    }
+   ],
+   "source": [
+    "MySpec('asd')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "stream",
+     "name": "stderr",
+     "text": [
+      "WARNING 2021-08-31 17:35:37,371 reporting.py(18) `RCausalModelEngine.__repr__` overrides interface `EstimationEngine.__repr__` without using the `@override` decorator.\n"
+     ]
+    },
+    {
+     "output_type": "error",
+     "ename": "AttributeError",
+     "evalue": "`SummaryEstimator.key` has not yet been assigned a value.",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-1-fb7a010d3034>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0;32mimport\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/__init__.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0msnapy\u001b[0m  \u001b[0;31m# noqa: F401; Import snapy before kragle to use snapy magics\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 6\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mbuilder\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mBuilder\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      7\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mhelpers\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mbuild_library\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      8\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpaths\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mBUILDERS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mMETRICS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mREPORTS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mSOURCES_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mQUERIES_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mFILTERS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mDIMENSIONS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mREPORT_CONFIGURATIONS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mCONFIG_SOURCES_DIR\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/__init__.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;34m\"\"\"Utility functions.\"\"\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0madd_on\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAddOn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0mafter_steps\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAfterExecutionStep\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0manalysis_context\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAnalysisContext\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0mconfig\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mCONFIG\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/add_on.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      6\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdimension\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mDimension\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 7\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmetric\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mMetric\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      8\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0merrors\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mValidationError\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/metric.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m     38\u001b[0m     \u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m'options'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     39\u001b[0m )\n\u001b[0;32m---> 40\u001b[0;31m \u001b[0;32mclass\u001b[0m \u001b[0mMetric\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mmetaclass\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mSubclassRegisteringMeta\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     41\u001b[0m     \"\"\"\n\u001b[1;32m     42\u001b[0m     \u001b[0mDefines\u001b[0m \u001b[0ma\u001b[0m \u001b[0mmetric\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/metric.py\u001b[0m in \u001b[0;36mMetric\u001b[0;34m()\u001b[0m\n\u001b[1;32m    187\u001b[0m     \u001b[0mcompression_overrides\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mDict\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mstr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mTerm\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m{\u001b[0m\u001b[0;34m}\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    188\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 189\u001b[0;31m     \u001b[0mmodels\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mList\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mModel\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m[\u001b[0m\u001b[0mDescriptiveStats\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mTTestStats\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    190\u001b[0m     \u001b[0mp_value_threshold\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mfloat\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;36m0.05\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    191\u001b[0m     \u001b[0mearly_stopping_alpha\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mOptional\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mfloat\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, key, data, engine, measure, link, hyperparams, estimations, label, visualizations, layout, compression_requirements, get_cell_significance, summary_estimators, treatment_effect_estimators, treatment_family_estimators, segment_by_covariates, summary_statistics, treatment_effect_statistics)\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36minit\u001b[0;34m(spec_cls, self, **kwargs)\u001b[0m\n\u001b[1;32m     85\u001b[0m                 \u001b[0;32mif\u001b[0m \u001b[0mcopy_required\u001b[0m \u001b[0;32mand\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0misinstance\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0mint\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mstr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtuple\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     86\u001b[0m                     \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mcopy\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdeepcopy\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 87\u001b[0;31m                 \u001b[0msetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     88\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     89\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0minstance_metadata\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__setattr__\u001b[0;34m(self, attr, value, force)\u001b[0m\n\u001b[1;32m    162\u001b[0m             \u001b[0mattr_spec\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__spec_class__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mattrs\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mget\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    163\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 164\u001b[0;31m                 \u001b[0mWithAttrMethod\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0m_inplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    165\u001b[0m                 \u001b[0;32mreturn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    166\u001b[0m             \u001b[0mmutate_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0minplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtype_check\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mforce\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mforce\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/scalar.py\u001b[0m in \u001b[0;36mwith_attr\u001b[0;34m(attr_spec, self, _new_value, _inplace, _if, **attrs)\u001b[0m\n\u001b[1;32m     29\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     30\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mis_collection\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 31\u001b[0;31m             _new_value = attr_spec.collection_mutator_type(\n\u001b[0m\u001b[1;32m     32\u001b[0m                 \u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtype\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mcollection\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0m_new_value\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mname\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     33\u001b[0m             ).prepare(item_preparer=functools.partial(attr_spec.prepare_item, self)).collection\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36mprepare\u001b[0;34m(self, item_preparer)\u001b[0m\n\u001b[1;32m     33\u001b[0m             \u001b[0mitems\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     34\u001b[0m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_create_collection\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 35\u001b[0;31m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0madd_items\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitems\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mitem_preparer\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     36\u001b[0m             \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     37\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;32mor\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mitem_preparer\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36madd_items\u001b[0;34m(self, items, preparer)\u001b[0m\n\u001b[1;32m     79\u001b[0m         \u001b[0mpreparer\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mpreparer\u001b[0m \u001b[0;32mor\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0;32mlambda\u001b[0m \u001b[0mitem\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     80\u001b[0m         \u001b[0;32mfor\u001b[0m \u001b[0mitem\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mitems\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 81\u001b[0;31m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0madd_item\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mpreparer\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     82\u001b[0m         \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     83\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36madd_item\u001b[0;34m(self, item, replace, attrs)\u001b[0m\n\u001b[1;32m     67\u001b[0m         ):\n\u001b[1;32m     68\u001b[0m             \u001b[0mitem\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mitem_spec_type\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 69\u001b[0;31m         return self._mutate_collection(\n\u001b[0m\u001b[1;32m     70\u001b[0m             \u001b[0mvalue_or_index\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     71\u001b[0m             \u001b[0mextractor\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_extractor\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/base.py\u001b[0m in \u001b[0;36m_mutate_collection\u001b[0;34m(self, value_or_index, extractor, inserter, require_pre_existent, new_item, transform, attrs, attr_transforms, replace, inplace)\u001b[0m\n\u001b[1;32m     73\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0mMISSING\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     74\u001b[0m             \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_create_collection\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 75\u001b[0;31m         index, old_item = extractor(\n\u001b[0m\u001b[1;32m     76\u001b[0m             \u001b[0mvalue_or_index\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mraise_if_missing\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mrequire_pre_existent\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     77\u001b[0m         )\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/collections/sets.py\u001b[0m in \u001b[0;36m_extractor\u001b[0;34m(self, value_or_index, raise_if_missing)\u001b[0m\n\u001b[1;32m     15\u001b[0m         return (\n\u001b[1;32m     16\u001b[0m             \u001b[0mvalue_or_index\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 17\u001b[0;31m             \u001b[0mvalue_or_index\u001b[0m \u001b[0;32mif\u001b[0m \u001b[0mvalue_or_index\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcollection\u001b[0m \u001b[0;32melse\u001b[0m \u001b[0mMISSING\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     18\u001b[0m         )\n\u001b[1;32m     19\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/types/keyed.py\u001b[0m in \u001b[0;36m__contains__\u001b[0;34m(self, item_or_key)\u001b[0m\n\u001b[1;32m    274\u001b[0m         \u001b[0;31m# Check whether item_or_key exists as a value\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    275\u001b[0m         \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 276\u001b[0;31m             \u001b[0mkey\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mkey\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem_or_key\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    277\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mkey\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m_dict\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    278\u001b[0m                 return (\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/types/keyed.py\u001b[0m in \u001b[0;36m__get_item_key\u001b[0;34m(self, item)\u001b[0m\n\u001b[1;32m     39\u001b[0m             \u001b[0mkey\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mitem\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__spec_class__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mkey\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     40\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mkey\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 41\u001b[0;31m                 \u001b[0;32mreturn\u001b[0m \u001b[0mgetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mkey\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     42\u001b[0m         \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     43\u001b[0m             \u001b[0mhash\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mitem\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__getattr__\u001b[0;34m(self, attr)\u001b[0m\n\u001b[1;32m    138\u001b[0m                 \u001b[0;32mand\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0minspect\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0misdatadescriptor\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mgetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__class__\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    139\u001b[0m             ):\n\u001b[0;32m--> 140\u001b[0;31m                 raise AttributeError(\n\u001b[0m\u001b[1;32m    141\u001b[0m                     \u001b[0;34mf\"`{self.__class__.__name__}.{attr}` has not yet been assigned a value.\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    142\u001b[0m                 )\n",
+      "\u001b[0;31mAttributeError\u001b[0m: `SummaryEstimator.key` has not yet been assigned a value."
+     ]
+    }
+   ],
+   "source": [
+    "import metrics_repo"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from spec_classes import spec_class, MISSING\n",
+    "from cached_property import cached_property\n",
+    "from typing import Dict, List, Set\n",
+    "from spec_classes.types import KeyedList"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "@spec_class\n",
+    "class MyClass:\n",
+    "    prepared_str: str = \"a\"\n",
+    "    prepared_items: List[str] = []\n",
+    "\n",
+    "    def _prepare_prepared_str(self, prepared_str):\n",
+    "        return \"c\"\n",
+    "\n",
+    "    def _prepare_prepared_item(self, prepared_item):\n",
+    "        return \"c\""
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 16,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "error",
+     "ename": "TypeError",
+     "evalue": "Attempt to set `MyClass.prepared_items` with an invalid type [got `'c'`; expecting `list[str]`].",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-16-f1ee700f6270>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mMyClass\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mprepared_str\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, prepared_str, prepared_items)\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36minit\u001b[0;34m(spec_cls, self, **kwargs)\u001b[0m\n\u001b[1;32m     83\u001b[0m                     \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mcopy\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdeepcopy\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     84\u001b[0m                 \u001b[0msetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 85\u001b[0;31m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     86\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0minstance_metadata\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     87\u001b[0m             getattr(self, f\"with_{instance_metadata.init_overflow_attr}\")(  # TODO: avoid this\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__setattr__\u001b[0;34m(self, attr, value, force)\u001b[0m\n\u001b[1;32m    160\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    161\u001b[0m                 \u001b[0mWithAttrMethod\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0m_inplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 162\u001b[0;31m                 \u001b[0;32mreturn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    163\u001b[0m             \u001b[0mmutate_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0minplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtype_check\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mforce\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mforce\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    164\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/scalar.py\u001b[0m in \u001b[0;36mwith_attr\u001b[0;34m(attr_spec, self, _new_value, _inplace, _if, **attrs)\u001b[0m\n\u001b[1;32m     40\u001b[0m             )\n\u001b[1;32m     41\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 42\u001b[0;31m         return mutate_attr(\n\u001b[0m\u001b[1;32m     43\u001b[0m             \u001b[0mobj\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     44\u001b[0m             \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/utils/mutation.py\u001b[0m in \u001b[0;36mmutate_attr\u001b[0;34m(obj, attr, value, inplace, type_check, force)\u001b[0m\n\u001b[1;32m     49\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mtype_check\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     50\u001b[0m                 \u001b[0;32mif\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mcheck_type\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtype\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 51\u001b[0;31m                     raise TypeError(\n\u001b[0m\u001b[1;32m     52\u001b[0m                         \u001b[0;34mf\"Attempt to set `{obj.__class__.__name__}.{attr}` with an invalid type [got `{repr(value)}`; expecting `{type_label(attr_spec.type)}`].\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     53\u001b[0m                     )\n",
+      "\u001b[0;31mTypeError\u001b[0m: Attempt to set `MyClass.prepared_items` with an invalid type [got `'c'`; expecting `list[str]`]."
+     ]
+    }
+   ],
+   "source": [
+    "MyClass().prepared_str"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "@spec_class\n",
+    "class Spec:\n",
+    "    attr: str = \"Hello\"\n",
+    "\n",
+    "@spec_class\n",
+    "class SubSpec(Spec):\n",
+    "    @property\n",
+    "    def attr(self):\n",
+    "        return \"World\""
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "execute_result",
+     "data": {
+      "text/plain": [
+       "__main__.SubSpec"
+      ]
+     },
+     "metadata": {},
+     "execution_count": 14
+    }
+   ],
+   "source": [
+    "SubSpec.__spec_class__.attrs['attr'].owner"
+   ]
+  },
+  {
+   "source": [
+    "@spec_class\n",
+    "class UnkeyedSpec:\n",
+    "    nested_scalar: int = 1\n",
+    "    nested_scalar2: str = \"original value\"\n",
+    "\n",
+    "\n",
+    "@spec_class(key=\"key\")\n",
+    "class KeyedSpec:\n",
+    "    key: str = \"key\"\n",
+    "    nested_scalar: int = 1\n",
+    "    nested_scalar2: str = \"original value\"\n",
+    "\n",
+    "\n",
+    "@spec_class(key=\"key\", bootstrap=True)\n",
+    "class Spec:\n",
+    "    key: str = \"key\"\n",
+    "    scalar: int\n",
+    "    list_values: List[int]\n",
+    "    dict_values: Dict[str, int]\n",
+    "    set_values: Set[str]\n",
+    "    spec: UnkeyedSpec\n",
+    "    spec_list_items: List[UnkeyedSpec]\n",
+    "    spec_dict_items: Dict[str, UnkeyedSpec]\n",
+    "    keyed_spec_list_items: List[KeyedSpec]\n",
+    "    keyed_spec_dict_items: Dict[str, KeyedSpec]\n",
+    "    recursive: \"Spec\""
+   ],
+   "cell_type": "code",
+   "metadata": {},
+   "execution_count": 2,
+   "outputs": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "\n",
+    "from spec_classes import spec_property\n",
+    "\n",
+    "@spec_class\n",
+    "class MySpecClass:\n",
+    "\n",
+    "    overridable_int: int\n",
+    "    static_str: str\n",
+    "    cached_time: float\n",
+    "    bad_typecheck: int\n",
+    "\n",
+    "    @spec_property\n",
+    "    def overridable_int(self):\n",
+    "        return 10\n",
+    "\n",
+    "    @spec_property(overridable=False)\n",
+    "    def static_str(self):\n",
+    "        return \"string\"\n",
+    "\n",
+    "    @spec_property(cache=True)\n",
+    "    def cached_time(self):\n",
+    "        import time\n",
+    "\n",
+    "        return time.time()\n",
+    "\n",
+    "    @spec_property\n",
+    "    def bad_typecheck(self):\n",
+    "        return \"string\"\n",
+    "\n",
+    "    no_methods = spec_property(None, overridable=False)\n",
+    "\n",
+    "    @spec_property\n",
+    "    def method_overrides(self):\n",
+    "        return\n",
+    "\n",
+    "    @method_overrides.getter\n",
+    "    def method_overrides(self):\n",
+    "        raise RuntimeError(\"In `method_overrides` getter.\")\n",
+    "\n",
+    "    @method_overrides.setter\n",
+    "    def method_overrides(self, method_overrides):\n",
+    "        raise RuntimeError(\"In `method_overrides` setter.\")\n",
+    "\n",
+    "    @method_overrides.deleter\n",
+    "    def method_overrides(self):\n",
+    "        raise RuntimeError(\"In `method_overrides` deleter.\")\n",
+    "\n",
+    "    @spec_property(cache=True, invalidated_by=[\"overridable_int\"])\n",
+    "    def invalidated_obj(self):\n",
+    "        return object()\n",
+    "\n",
+    "    @spec_property(cache=True, invalidated_by=\"*\")\n",
+    "    def always_invalidated_obj(self):\n",
+    "        return object()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "spec_cls = MySpecClass()\n",
+    "spec_cls.overridable_int = 10\n",
+    "spec_cls.invalidated_obj\n",
+    "\n",
+    "obj = spec_cls.invalidated_obj\n",
+    "aobj = spec_cls.always_invalidated_obj"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "execute_result",
+     "data": {
+      "text/plain": [
+       "{'overridable_int': <spec_classes.types.attr.Attr at 0x7f6773743fa0>,\n",
+       " 'static_str': <spec_classes.types.attr.Attr at 0x7f6773743e80>,\n",
+       " 'cached_time': <spec_classes.types.attr.Attr at 0x7f6773743790>,\n",
+       " 'bad_typecheck': <spec_classes.types.attr.Attr at 0x7f67737437c0>}"
+      ]
+     },
+     "metadata": {},
+     "execution_count": 8
+    }
+   ],
+   "source": [
+    "spec_cls.__spec_class__.attrs"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "error",
+     "ename": "AssertionError",
+     "evalue": "",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAssertionError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-7-b059beb0fac8>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;32mdel\u001b[0m \u001b[0mspec_cls\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0moverridable_int\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0;32massert\u001b[0m \u001b[0mspec_cls\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minvalidated_obj\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mobj\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0;32massert\u001b[0m \u001b[0mspec_cls\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0malways_invalidated_obj\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0maobj\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mAssertionError\u001b[0m: "
+     ]
+    }
+   ],
+   "source": [
+    "\n",
+    "\n",
+    "del spec_cls.overridable_int\n",
+    "assert spec_cls.invalidated_obj is not obj\n",
+    "assert spec_cls.always_invalidated_obj is not aobj"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "stream",
+     "name": "stderr",
+     "text": [
+      "WARNING 2021-08-30 17:16:27,337 reporting.py(18) `RCausalModelEngine.__repr__` overrides interface `EstimationEngine.__repr__` without using the `@override` decorator.\n"
+     ]
+    },
+    {
+     "output_type": "error",
+     "ename": "AttributeError",
+     "evalue": "Cannot set `DescriptiveStats.compression_requirements` to `CompressionRequirements(\n    statistics={\n        'count',\n        'sos',\n        'sum'\n    },\n    grains=set(),\n    include_quantile_extents=False,\n    long_form=False\n)`. Is this a property without a setter?",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/utils/mutation.py\u001b[0m in \u001b[0;36mmutate_attr\u001b[0;34m(obj, attr, value, inplace, type_check, force)\u001b[0m\n\u001b[1;32m     60\u001b[0m     \u001b[0;32mtry\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 61\u001b[0;31m         \u001b[0mgetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__setattr__\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m\"__raw__\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0msetattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mobj\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     62\u001b[0m     \u001b[0;32mexcept\u001b[0m \u001b[0mAttributeError\u001b[0m \u001b[0;32mas\u001b[0m \u001b[0me\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mAttributeError\u001b[0m: can't set attribute",
+      "\nThe above exception was the direct cause of the following exception:\n",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-1-fb7a010d3034>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0;32mimport\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/__init__.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0msnapy\u001b[0m  \u001b[0;31m# noqa: F401; Import snapy before kragle to use snapy magics\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 6\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mbuilder\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mBuilder\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      7\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mhelpers\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mbuild_library\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      8\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpaths\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mBUILDERS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mMETRICS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mREPORTS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mSOURCES_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mQUERIES_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mFILTERS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mDIMENSIONS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mREPORT_CONFIGURATIONS_DIR\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mCONFIG_SOURCES_DIR\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/__init__.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[0;34m\"\"\"Utility functions.\"\"\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 2\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0madd_on\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAddOn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      3\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0mafter_steps\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAfterExecutionStep\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      4\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0manalysis_context\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mAnalysisContext\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0mconfig\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mCONFIG\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/add_on.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m      5\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      6\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdimension\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mDimension\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m----> 7\u001b[0;31m \u001b[0;32mfrom\u001b[0m \u001b[0mmetrics_repo\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mlib\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mmetric\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mMetric\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      8\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m      9\u001b[0m \u001b[0;32mfrom\u001b[0m \u001b[0;34m.\u001b[0m\u001b[0merrors\u001b[0m \u001b[0;32mimport\u001b[0m \u001b[0mValidationError\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/metric.py\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[1;32m     38\u001b[0m     \u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m'options'\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     39\u001b[0m )\n\u001b[0;32m---> 40\u001b[0;31m \u001b[0;32mclass\u001b[0m \u001b[0mMetric\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mmetaclass\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mSubclassRegisteringMeta\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     41\u001b[0m     \"\"\"\n\u001b[1;32m     42\u001b[0m     \u001b[0mDefines\u001b[0m \u001b[0ma\u001b[0m \u001b[0mmetric\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/netflix/metrics-repo/metrics_repo/lib/metric.py\u001b[0m in \u001b[0;36mMetric\u001b[0;34m()\u001b[0m\n\u001b[1;32m    187\u001b[0m     \u001b[0mcompression_overrides\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mDict\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mstr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mTerm\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m{\u001b[0m\u001b[0;34m}\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    188\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 189\u001b[0;31m     \u001b[0mmodels\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mList\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mModel\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;34m[\u001b[0m\u001b[0mDescriptiveStats\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mTTestStats\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m]\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    190\u001b[0m     \u001b[0mp_value_threshold\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mfloat\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;36m0.05\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    191\u001b[0m     \u001b[0mearly_stopping_alpha\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mOptional\u001b[0m\u001b[0;34m[\u001b[0m\u001b[0mfloat\u001b[0m\u001b[0;34m]\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, key, data, engine, measure, link, hyperparams, estimations, label, visualizations, layout, compression_requirements, get_cell_significance, summary_estimators, treatment_effect_estimators, treatment_family_estimators, segment_by_covariates, summary_statistics, treatment_effect_statistics)\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36minit\u001b[0;34m(spec_cls, self, **kwargs)\u001b[0m\n\u001b[1;32m     30\u001b[0m             \u001b[0mparent_metadata\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mgetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mparent\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m\"__spec_class__\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mNone\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     31\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mparent_metadata\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 32\u001b[0;31m                 parent.__init__(self, **{\n\u001b[0m\u001b[1;32m     33\u001b[0m                     \u001b[0mattr\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mkwargs\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpop\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     34\u001b[0m                     \u001b[0;32mfor\u001b[0m \u001b[0mattr\u001b[0m \u001b[0;32min\u001b[0m \u001b[0mlist\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mkwargs\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, key, data, engine, measure, link, hyperparams, estimations, label, visualizations, layout, compression_requirements, get_cell_significance, summary_estimators, treatment_effect_estimators, treatment_family_estimators, segment_by_covariates, summary_statistics, treatment_effect_statistics)\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36minit\u001b[0;34m(spec_cls, self, **kwargs)\u001b[0m\n\u001b[1;32m     77\u001b[0m                 \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mcopy\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdeepcopy\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     78\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mvalue\u001b[0m \u001b[0;32mis\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0mMISSING\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 79\u001b[0;31m                 \u001b[0msetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     80\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     81\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mmetadata\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__setattr__\u001b[0;34m(self, attr, value, force)\u001b[0m\n\u001b[1;32m    154\u001b[0m             \u001b[0mattr_spec\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__spec_class__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mattrs\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mget\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    155\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 156\u001b[0;31m                 \u001b[0mWithAttrMethod\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0m_inplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    157\u001b[0m                 \u001b[0;32mreturn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    158\u001b[0m             \u001b[0mmutate_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0minplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtype_check\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mforce\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mforce\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/scalar.py\u001b[0m in \u001b[0;36mwith_attr\u001b[0;34m(attr_spec, self, _new_value, _inplace, _if, **attrs)\u001b[0m\n\u001b[1;32m     40\u001b[0m             )\n\u001b[1;32m     41\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 42\u001b[0;31m         return mutate_attr(\n\u001b[0m\u001b[1;32m     43\u001b[0m             \u001b[0mobj\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     44\u001b[0m             \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mname\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/utils/mutation.py\u001b[0m in \u001b[0;36mmutate_attr\u001b[0;34m(obj, attr, value, inplace, type_check, force)\u001b[0m\n\u001b[1;32m     62\u001b[0m     \u001b[0;32mexcept\u001b[0m \u001b[0mAttributeError\u001b[0m \u001b[0;32mas\u001b[0m \u001b[0me\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     63\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0me\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0margs\u001b[0m \u001b[0;34m==\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0;34m\"can't set attribute\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m  \u001b[0;31m# Let's make this error less obtuse.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 64\u001b[0;31m             raise AttributeError(\n\u001b[0m\u001b[1;32m     65\u001b[0m                 \u001b[0;34mf\"Cannot set `{obj.__class__.__name__}.{attr}` to `{value}`. Is this a property without a setter?\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     66\u001b[0m             ) from e\n",
+      "\u001b[0;31mAttributeError\u001b[0m: Cannot set `DescriptiveStats.compression_requirements` to `CompressionRequirements(\n    statistics={\n        'count',\n        'sos',\n        'sum'\n    },\n    grains=set(),\n    include_quantile_extents=False,\n    long_form=False\n)`. Is this a property without a setter?"
+     ]
+    }
+   ],
+   "source": [
+    "import metrics_repo"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "execute_result",
+     "data": {
+      "text/plain": [
+       "UnkeyedSpec(nested_scalar=1, nested_scalar2='original value')"
+      ]
+     },
+     "metadata": {},
+     "execution_count": 3
+    }
+   ],
+   "source": [
+    "UnkeyedSpec()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from spec_classes.utils.type_checking import get_spec_class_for_type"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "get_spec_class_for_type(UnkeyedSpec)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "stream",
+     "name": "stdout",
+     "text": [
+      "transform_spec spec <class '__main__.UnkeyedSpec'> None\n"
+     ]
+    },
+    {
+     "output_type": "error",
+     "ename": "TypeError",
+     "evalue": "transform_spec() missing 1 required positional argument: '_transform'",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-5-58be7063fcc0>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mSpec\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_spec\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtransform_spec\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mnested_scalar\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mlambda\u001b[0m \u001b[0mx\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mx\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_nested_scalar\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m3\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m: transform_spec() missing 1 required positional argument: '_transform'"
+     ]
+    }
+   ],
+   "source": [
+    "Spec().with_spec().transform_spec(nested_scalar=lambda x: x.with_nested_scalar(3))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {
+    "tags": [
+     "outputPrepend"
+    ]
+   },
+   "outputs": [
+    {
+     "output_type": "stream",
+     "name": "stdout",
+     "text": [
+      "SSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.UnkeyedSpec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 1, 'constructor': <class 'int'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'original value', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class '__main__.Spec'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': 'key', 'constructor': <class 'str'>, 'attrs': {}}\n",
+      "{'old_value': MISSING, 'new_value': MISSING, 'constructor': <class 'int'>, 'attrs': {}}\n"
+     ]
+    },
+    {
+     "output_type": "error",
+     "ename": "RecursionError",
+     "evalue": "maximum recursion depth exceeded in comparison",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mRecursionError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-15-7df682be545e>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mSpec\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mkey\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;34m'a'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, key, scalar, list_values, dict_values, set_values, spec, spec_list_items, spec_dict_items, keyed_spec_list_items, keyed_spec_dict_items, recursive)\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36minit\u001b[0;34m(self, **kwargs)\u001b[0m\n\u001b[1;32m     73\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mcopy_required\u001b[0m \u001b[0;32mand\u001b[0m \u001b[0;32mnot\u001b[0m \u001b[0misinstance\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;34m(\u001b[0m\u001b[0mint\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mstr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtuple\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     74\u001b[0m                 \u001b[0mvalue\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mcopy\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mdeepcopy\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m---> 75\u001b[0;31m             \u001b[0msetattr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     76\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     77\u001b[0m         \u001b[0;32mif\u001b[0m \u001b[0mmetadata\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0minit_overflow_attr\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__setattr__\u001b[0;34m(self, attr, value, force)\u001b[0m\n\u001b[1;32m    150\u001b[0m             \u001b[0mattr_spec\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__spec_class__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mattrs\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mget\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    151\u001b[0m             \u001b[0;32mif\u001b[0m \u001b[0mattr_spec\u001b[0m\u001b[0;34m:\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 152\u001b[0;31m                 \u001b[0mWithAttrMethod\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mattr_spec\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0m_inplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    153\u001b[0m                 \u001b[0;32mreturn\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    154\u001b[0m             \u001b[0mmutate_attr\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattr\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mvalue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0minplace\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mtype_check\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;32mTrue\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mforce\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mforce\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/scalar.py\u001b[0m in \u001b[0;36mwith_attr\u001b[0;34m(attr_spec, self, _new_value, _inplace, _if, **attrs)\u001b[0m\n\u001b[1;32m     39\u001b[0m                 \u001b[0mattrs\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mattrs\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m     40\u001b[0m             )\n\u001b[0;32m---> 41\u001b[0;31m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m     42\u001b[0m         return mutate_attr(\n\u001b[1;32m     43\u001b[0m             \u001b[0mobj\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/utils/mutation.py\u001b[0m in \u001b[0;36mmutate_value\u001b[0;34m(old_value, new_value, replace, constructor, attrs, transform, attr_transforms)\u001b[0m\n\u001b[1;32m    154\u001b[0m             \u001b[0mconstructor\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mconstructor\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__origin__\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    155\u001b[0m         \u001b[0mconstructor_args\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0m_get_function_args\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mconstructor\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattrs\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0;32m--> 156\u001b[0;31m         value = constructor(\n\u001b[0m\u001b[1;32m    157\u001b[0m             **{\n\u001b[1;32m    158\u001b[0m                 \u001b[0mattr\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0mvalue\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "... last 5 frames repeated, from the frame below ...\n",
+      "\u001b[0;32m<string>\u001b[0m in \u001b[0;36m__init__\u001b[0;34m(self, key, scalar, list_values, dict_values, set_values, spec, spec_list_items, spec_dict_items, keyed_spec_list_items, keyed_spec_dict_items, recursive)\u001b[0m\n",
+      "\u001b[0;31mRecursionError\u001b[0m: maximum recursion depth exceeded in comparison"
+     ]
+    }
+   ],
+   "source": [
+    "Spec(key='a')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "@spec_class(bootstrap=True)\n",
+    "class MySpec:\n",
+    "    #data: Dict[str, int] = {}\n",
+    "    items: List[int] = []\n",
+    "\n",
+    "    def _prepare_item(self, s, **attrs):\n",
+    "        return int(s)\n",
+    "\n",
+    "    # def _prepare_datum(self, k, v):\n",
+    "    #     print(k, v)\n",
+    "    #     return k, v"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "execute_result",
+     "data": {
+      "text/plain": [
+       "<function __main__.MySpec._prepare_item(self, s, **attrs)>"
+      ]
+     },
+     "metadata": {},
+     "execution_count": 7
+    }
+   ],
+   "source": [
+    "MySpec.__spec_class__.attrs['items'].prepare_item"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 8,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "execute_result",
+     "data": {
+      "text/plain": [
+       "MySpec(items=[1, 2, 3])"
+      ]
+     },
+     "metadata": {},
+     "execution_count": 8
+    }
+   ],
+   "source": [
+    "MySpec(items=['1', '2', '3'])"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "stream",
+     "name": "stdout",
+     "text": [
+      "<bound method Attr.item_preparer of <spec_classes.spec_class.Attr object at 0x7fd9d803b0d0>>\n"
+     ]
+    },
+    {
+     "output_type": "error",
+     "ename": "AttributeError",
+     "evalue": "'MySpec' object has no attribute 'with_datum'",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mAttributeError\u001b[0m                            Traceback (most recent call last)",
+      "\u001b[0;32m<ipython-input-5-1a993c4c2413>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mMySpec\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwith_datum\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'a'\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mtransform_datum\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m\"a\"\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0;32mlambda\u001b[0m \u001b[0mx\u001b[0m\u001b[0;34m:\u001b[0m \u001b[0;36m2\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mwithout_datum\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m'a'\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
+      "\u001b[0;32m~/Repositories/github/spec-classes/spec_classes/methods/core.py\u001b[0m in \u001b[0;36m__getattr__\u001b[0;34m(self, attr)\u001b[0m\n\u001b[1;32m    129\u001b[0m                     \u001b[0;34mf\"`{self.__class__.__name__}.{attr}` has not yet been assigned a value.\"\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    130\u001b[0m                 )\n\u001b[0;32m--> 131\u001b[0;31m             \u001b[0;32mreturn\u001b[0m \u001b[0mself\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__getattr__\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0m__raw__\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mself\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mattr\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m    132\u001b[0m \u001b[0;34m\u001b[0m\u001b[0m\n\u001b[1;32m    133\u001b[0m         \u001b[0;31m# Add reference to original __getattr__ method.\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
+      "\u001b[0;31mAttributeError\u001b[0m: 'MySpec' object has no attribute 'with_datum'"
+     ]
+    }
+   ],
+   "source": [
+    "MySpec().with_datum('a', 1).transform_datum(\"a\", lambda x: 2).without_datum('a')"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 4,
+   "metadata": {},
+   "outputs": [
+    {
+     "output_type": "stream",
+     "name": "stdout",
+     "text": [
+      "Help on method transform_datum:\n\ntransform_datum(_key: str, _transform: Callable, *, _inplace: bool = False, _if: bool = True) method of __main__.MySpec instance\n    Return a `MySpec` instance identical to this one except with an item transformed in `data`.\n    \n    Args:\n        _key: The key for the item to be inserted or updated.\n        _transform: A function that takes the old item as input, and returns\n            the new item.\n        _inplace: Whether to perform change without first copying.\n        _if: This action is only taken when `_if` is `True`. If it is `False`,\n            this is a no-op.\n    Returns:\n        A reference to the mutated `MySpec` instance.\n\n"
+     ]
+    }
+   ],
+   "source": [
+    "help(MySpec().transform_datum)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ]
+}
\ No newline at end of file
diff --git a/spec_classes/__init__.py b/spec_classes/__init__.py
index fad8084..6244c8c 100644
--- a/spec_classes/__init__.py
+++ b/spec_classes/__init__.py
@@ -1,8 +1,12 @@
-from ._version import __version__, __version_tuple__
 from .errors import FrozenInstanceError
 from .spec_class import spec_class
 from .types import Alias, DeprecatedAlias, Attr, AttrProxy, MISSING, spec_property
 
+try:
+    from ._version import __version__, __version_tuple__
+except ImportError:
+    __version__ = __version_tuple__ = None
+
 __author__ = "Matthew Wardrop"
 __author_email__ = "mpwardrop@gmail.com"
 
diff --git a/spec_classes/methods/core.py b/spec_classes/methods/core.py
index b45183f..4a6ce64 100644
--- a/spec_classes/methods/core.py
+++ b/spec_classes/methods/core.py
@@ -8,7 +8,7 @@
 
 from spec_classes.errors import FrozenInstanceError
 from spec_classes.methods.scalar import WithAttrMethod
-from spec_classes.types import Attr, MISSING
+from spec_classes.types import Attr, MISSING, UNSPECIFIED
 from spec_classes.utils.method_builder import MethodBuilder
 from spec_classes.utils.mutation import (
     invalidate_attrs,
@@ -16,9 +16,11 @@
     protect_via_deepcopy,
 )
 
-from .base import MethodDescriptor
+from spec_classes.methods.base import MethodDescriptor
 
 
+MISSING_FINAL = object()
+
 class InitMethod(MethodDescriptor):
     """
     The default implementation of `__init__` for spec-classes.
@@ -39,92 +41,96 @@ class InitMethod(MethodDescriptor):
 
     method_name = "__init__"
 
+
     @staticmethod
-    def init(spec_cls, self, **kwargs):
-        instance_metadata = self.__spec_class__
+    def build_init_method_body(spec_cls):
+        metadata = spec_cls.__spec_class__
+        body = [
+            "metadata = self.__spec_class__",
+        ]
+
+        for attr, attr_spec in metadata.attrs.items():
+            body.append(f"""
+                if {attr} is UNSPECIFIED:
+                    {attr} = metadata.attrs['{attr}'].get_value(self.__class__, {attr}, copy={not attr_spec.do_not_copy})
+            """)
 
         # Unlock the class for mutation during initialization.
-        is_frozen = instance_metadata.frozen
-        if instance_metadata.owner is spec_cls and instance_metadata.frozen:
-            instance_metadata.frozen = False
+        is_frozen = metadata.frozen
+        if metadata.owner is spec_cls and metadata.frozen:
+            body.append("metadata.frozen = False")
 
         # Initialise any non-local spec attributes via parent constructors
-        if instance_metadata.owner is spec_cls:
-            for parent in reversed(spec_cls.mro()[1:]):
+        if metadata.owner is spec_cls:
+            for parent_index, parent in enumerate(reversed(spec_cls.mro()[1:])):
                 parent_metadata = getattr(parent, "__spec_class__", None)
                 if parent_metadata:
-                    parent_kwargs = {}
+                    parent_args = []
                     for attr in parent_metadata.attrs:
-                        instance_attr_spec = instance_metadata.attrs[attr]
-                        if instance_attr_spec.owner is not parent:
+                        attr_spec = metadata.attrs[attr]
+                        if attr_spec.owner is not parent:
                             continue
-                        if attr in kwargs:
-                            parent_kwargs[attr] = kwargs.pop(attr)
-                        else:
-                            # Parent constructor may may be overridden, and not pick up
-                            # subclass defaults. We pre-emptively solve this here.
-                            # If the constructor was not overridden, then no harm is
-                            # done (we just looked it up earlier than we had to).
-                            # We don't pass missing values in case overridden constructor
-                            # has defaults in the signature.
-                            instance_default = instance_attr_spec.lookup_default_value(
-                                self.__class__
-                            )
-                            if instance_default is not MISSING:
-                                parent_kwargs[attr] = instance_default
-                    if parent_metadata.key and parent_metadata.key not in parent_kwargs:
-                        parent_kwargs[parent_metadata.key] = MISSING
-                    parent.__init__(  # pylint: disable=unnecessary-dunder-call
-                        self, **parent_kwargs
-                    )
-
-        # For each attribute owned by this spec_cls in `instance_metadata`,
+                        parent_args.append(f""""{attr}": {attr},""")
+                    if parent_metadata.key and parent_metadata.key not in parent_args:
+                        parent_args.append(f""""{parent_metadata.key}": MISSING if {parent_metadata.key} is UNSPECIFIED else MISSING""")
+                    parent_args = "".join(parent_args)
+                    body.append(f"""
+                        self.__class__.mro()[-{parent_index+1}].__init__(self, **{{k: v for k, v in {{{parent_args}}}.items() if v is not UNSPECIFIED }})
+                    """)
+
+        # For each attribute owned by this spec_cls in `metadata`,
         # initalize the attribute.
-        for attr, attr_spec in instance_metadata.attrs.items():
+        for attr, attr_spec in metadata.attrs.items():
+
             if (
                 not attr_spec.init
                 or attr_spec.owner is not spec_cls
-                or attr == instance_metadata.init_overflow_attr
+                or attr == metadata.init_overflow_attr
             ):
                 continue
 
-            value = kwargs.get(attr, MISSING)
-            if value is not MISSING:
-                # If owner is not spec-class, we have already looked up and
-                # handled copying.
-                copy_required = (
-                    instance_metadata.owner is spec_cls and not attr_spec.do_not_copy
-                )
-            else:
-                value = attr_spec.lookup_default_value(self.__class__)
-                copy_required = False
-
-            if value is not MISSING:
-                if copy_required:
-                    value = protect_via_deepcopy(value)
-                setattr(self, attr, value)
+            copy_required = metadata.owner is spec_cls and not attr_spec.do_not_copy
+
+            body.append(f"""
+                # Assign `{attr}`
+                # {attr} = metadata.attrs['{attr}'].get_value(self.__class__, {attr}, copy={copy_required})
+                if {attr} not in (MISSING, UNSPECIFIED):
+                    self.{attr} = {attr}
+            """)
+            # if copy_required:
+            #     body.append(f"""
+            #     if {attr} is not MISSING:
+            #         {attr} = protect_via_deepcopy({attr})
+            #     """)
+
+            # body.append(f"""
+            #     if {attr} is MISSING:
+            #         {attr} = metadata.attrs['{attr}'].lookup_default_value(self.__class__)
+            #     if {attr} is not MISSING:
+            #         self.{attr} = {attr}
+            # """)
 
         # Finalize initialisation by storing overflow attrs and restoring frozen
         # status.
-        if instance_metadata.owner is spec_cls:
-            if instance_metadata.init_overflow_attr:
-                getattr(
-                    self, f"with_{instance_metadata.init_overflow_attr}"
-                )(  # TODO: avoid this
-                    {
-                        key: value
-                        for key, value in kwargs.items()
-                        if key not in instance_metadata.annotations
-                        or key == instance_metadata.init_overflow_attr
-                    },
-                    _inplace=True,
-                )
+        if metadata.owner is spec_cls:
+            if metadata.init_overflow_attr:
+                body.append(f"""
+                    self.with_{metadata.init_overflow_attr}({{ key: value for key, value in {metadata.init_overflow_attr}.items()
+                        if key not in metadata.annotations
+                        or key == metadata.init_overflow_attr }}, _inplace=True)
+                """)
 
-            if instance_metadata.post_init:
-                instance_metadata.post_init(self)
+            if metadata.post_init:
+                body.append("metadata.post_init(self)")
 
             if is_frozen:
-                instance_metadata.frozen = True
+                body.append("metadata.frozen = True")
+
+        return "\n".join(
+            textwrap.dedent(s)
+            for s in body
+        )
+
 
     def build_method(self) -> Callable:
         spec_class_key = self.spec_cls.__spec_class__.key
@@ -136,11 +142,11 @@ def build_method(self) -> Callable:
             # If the key has a default, don't require it to be set during
             # construction.
             key_default = (
-                MISSING if spec_class_key_spec.has_default else inspect.Parameter.empty
+                UNSPECIFIED if spec_class_key_spec.has_default else inspect.Parameter.empty
             )
 
         return (
-            MethodBuilder("__init__", functools.partial(self.init, self.spec_cls))
+            MethodBuilder("__init__", self.build_init_method_body(self.spec_cls), {"UNSPECIFIED": UNSPECIFIED, "MISSING": MISSING, "protect_via_deepcopy": protect_via_deepcopy})
             .with_preamble(f"Initialise this `{self.spec_cls.__name__}` instance.")
             .with_arg(
                 spec_class_key,
diff --git a/spec_classes/types/__init__.py b/spec_classes/types/__init__.py
index ae6d0ff..f201ef1 100644
--- a/spec_classes/types/__init__.py
+++ b/spec_classes/types/__init__.py
@@ -2,7 +2,7 @@
 from .attr import Attr
 from .attr_proxy import AttrProxy
 from .keyed import KeyedList, KeyedSet
-from .missing import MISSING
+from .missing import MISSING, UNSPECIFIED
 from .spec_property import spec_property
 from .validated import ValidatedType, bounded, validated
 
@@ -14,6 +14,7 @@
     "KeyedList",
     "KeyedSet",
     "MISSING",
+    "UNSPECIFIED",
     "ValidatedType",
     "bounded",
     "spec_property",
diff --git a/spec_classes/types/attr.py b/spec_classes/types/attr.py
index fd99f56..953945e 100644
--- a/spec_classes/types/attr.py
+++ b/spec_classes/types/attr.py
@@ -17,7 +17,7 @@
     type_match,
 )
 
-from .missing import MISSING
+from .missing import MISSING, UNSPECIFIED
 
 if TYPE_CHECKING:  # pragma: no cover
     from spec_classes.collections.base import CollectionAttrMutator
@@ -272,6 +272,21 @@ def item_constructor(self) -> Optional[Type]:
         return self.item_spec_type_polymorphic or self.item_type
 
     # Helpers
+
+    def get_value(self, spec_cls: Type, value: Any = UNSPECIFIED, copy: bool = True) -> Any:
+        from spec_classes.utils.mutation import protect_via_deepcopy
+
+        if value is MISSING:
+            return value
+        if value is UNSPECIFIED:
+            value = self.lookup_default_value(spec_cls)
+            if value is MISSING:
+                return UNSPECIFIED
+            return value
+        return protect_via_deepcopy(value) if copy else value
+
+
+
     def lookup_default_value(self, spec_cls: Type) -> Any:
         """
         Look up the correct default value for this attribute for `instance`.
diff --git a/spec_classes/types/missing.py b/spec_classes/types/missing.py
index 0f0551f..22d2711 100644
--- a/spec_classes/types/missing.py
+++ b/spec_classes/types/missing.py
@@ -1,17 +1,20 @@
 # Sentinel for unset inputs to spec_class methods
 class _MissingType:
-    __instance__ = None
+    __instances__ = {}
 
-    def __new__(cls):
-        if cls.__instance__ is None:
-            cls.__instance__ = super(_MissingType, cls).__new__(cls)
-        return cls.__instance__
+    def __new__(cls, name="MISSING"):
+        if name not in cls.__instances__:
+            cls.__instances__[name] = super(_MissingType, cls).__new__(cls)
+        return cls.__instances__[name]
+
+    def __init__(self, name="MISSING"):
+        self.name = name
 
     def __bool__(self):
         return False
 
     def __repr__(self):
-        return "MISSING"
+        return self.name
 
     def __copy__(self):
         return self
@@ -21,3 +24,4 @@ def __deepcopy__(self, memo):
 
 
 MISSING = _MissingType()
+UNSPECIFIED = _MissingType("UNSPECIFIED")
diff --git a/spec_classes/utils/method_builder.py b/spec_classes/utils/method_builder.py
index 467fd4f..220ef6a 100644
--- a/spec_classes/utils/method_builder.py
+++ b/spec_classes/utils/method_builder.py
@@ -1,11 +1,12 @@
 from __future__ import annotations
 
 import inspect
+import linecache
 import textwrap
 from inspect import Parameter, Signature, cleandoc
 from typing import Any, Callable, Dict, List, Optional, Tuple, Type, Union
 
-from spec_classes.types import MISSING
+from spec_classes.types import MISSING, UNSPECIFIED
 from spec_classes.utils.type_checking import type_label
 
 
@@ -60,9 +61,10 @@ class MethodBuilder:
 
     """
 
-    def __init__(self, name: str, implementation: Callable):
+    def __init__(self, name: str, implementation: Union[str, Callable], exec_context: Optional[Dict[str, Any]] = None):
         self.name = name
         self.implementation = implementation
+        self.exec_context = exec_context
 
         # Documentation attributes
         self.doc_preamble: str = ""
@@ -231,7 +233,7 @@ def with_args(
                 name,
                 desc=desc,
                 annotation=(annotations or {}).get(name, Parameter.empty),
-                default=(defaults or {}).get(name, MISSING),
+                default=(defaults or {}).get(name, UNSPECIFIED),
                 kind=Parameter.KEYWORD_ONLY,
                 virtual=virtual,
             )
@@ -285,7 +287,7 @@ def with_spec_attrs_for(
                 else attr_spec.desc
             )
             annotations[attr] = attr_spec.type
-            defaults[attr] = MISSING if attr_spec.is_masked else attr_spec.default
+            defaults[attr] = UNSPECIFIED if attr_spec.is_masked else attr_spec.lookup_default_value(spec_cls)
 
         self.with_args(
             args=args,
@@ -388,48 +390,90 @@ def build(self) -> Callable:
         namespace = {}
 
         signature = self._signature
-        impl_signature = Signature.from_callable(self.implementation)
         signature_advertised = (
             self._signature_virtual if self.method_args_virtual else signature
         )
+        str_signature, defaults = self._method_signature_to_definition_str(
+            signature_advertised
+            if isinstance(self.implementation, str)
+            else signature
+        )
 
-        if not self._check_signature_compatible_with_implementation(
-            signature, impl_signature
-        ):
-            raise RuntimeError(
-                f"Proposed method signature `{self.name}{signature}` is not compatible with implementation signature `implementation{impl_signature}`."
-            )
-
-        VALID_KWARGS = {p.name for p in self.method_args_virtual}
-
-        def validate_attrs(attrs):
-            for attr in attrs:
-                if attr not in VALID_KWARGS:
-                    extra_attrs = set(attrs)
-                    extra_attrs.difference_update(VALID_KWARGS)
-                    raise TypeError(
-                        f"{self.name}() got unexpected keyword arguments: {repr(extra_attrs)}."
-                    )
-
-        str_signature, defaults = self._method_signature_to_definition_str(signature)
+        if not isinstance(self.implementation, str):
+            impl_signature = Signature.from_callable(self.implementation)
+            if not self._check_signature_compatible_with_implementation(
+                signature, impl_signature
+            ):
+                raise RuntimeError(
+                    f"Proposed method signature `{self.name}{signature}` is not compatible with implementation signature `implementation{impl_signature}`."
+                )
 
-        exec(
-            textwrap.dedent(
+            VALID_KWARGS = {p.name for p in self.method_args_virtual}
+
+            def validate_attrs(attrs):
+                for attr in attrs:
+                    if attr not in VALID_KWARGS:
+                        extra_attrs = set(attrs)
+                        extra_attrs.difference_update(VALID_KWARGS)
+                        raise TypeError(
+                            f"{self.name}() got unexpected keyword arguments: {repr(extra_attrs)}."
+                        )
+
+            exec(
+                textwrap.dedent(
+                    f"""
+                from __future__ import annotations
+                def {self.name}{str_signature} { '-> ' + repr(type_label(self.method_return_type)) if self.method_return_type is not None else ""}:
+                    {"validate_attrs(kwargs)" if self.method_args_virtual and self.check_attrs_match_sig else ""}
+                    return implementation({self._method_signature_to_implementation_call(self._signature)})
+            """
+                ),
+                {
+                    "implementation": self.implementation,
+                    "MISSING": MISSING,
+                    "UNSPECIFIED": UNSPECIFIED,
+                    "validate_attrs": validate_attrs,
+                    "DEFAULTS": defaults,
+                },
+                namespace,
+            )
+        else:
+            import hashlib
+            function_source = textwrap.dedent(
                 f"""
             from __future__ import annotations
-            def {self.name}{str_signature} { '-> ' + repr(type_label(self.method_return_type)) if self.method_return_type is not None else ""}:
-                {"validate_attrs(kwargs)" if self.method_args_virtual and self.check_attrs_match_sig else ""}
-                return implementation({self._method_signature_to_implementation_call(self._signature)})
+            def {self.name}{self._signature_without_annotations} { '-> ' + repr(type_label(self.method_return_type)) if self.method_return_type is not None else ""}:
+{textwrap.indent(self.implementation, "                ")}
         """
-            ),
-            {
-                "implementation": self.implementation,
-                "MISSING": MISSING,
-                "validate_attrs": validate_attrs,
-                "DEFAULTS": defaults,
-            },
-            namespace,
-        )
+            )
+            source_hash = hashlib.sha256(function_source.encode()).hexdigest()
+            fake_source_file = f"spec_classes/{source_hash}.py"
+            print(function_source, defaults)
+
+            # In order of debuggers like PDB being able to step through the code,
+            # we add a fake linecache entry.
+            count = 1
+            filename = fake_source_file
+            while True:
+                linecache_tuple = (
+                    len(function_source),
+                    None,
+                    function_source.splitlines(True),
+                    filename,
+                )
+                old_val = linecache.cache.setdefault(fake_source_file, linecache_tuple)
+                if old_val == linecache_tuple:
+                    break
+                else:
+                    filename = f"{filename[:-1]}-{count}>"
+                    count += 1
+
+            code = compile(function_source, filename, "exec")
+            exec(code,  {
+                    **self.exec_context,
+                    "DEFAULTS": defaults,
+                },
+                namespace,)
 
         method = namespace[self.name]
         method.__doc__ = self._docstring
@@ -458,6 +502,19 @@ def _signature_virtual(self) -> Signature:
             self._signature
         )  # pragma: no cover; we avoid this case in the code to running this twice
 
+    @property
+    def _signature_without_annotations(self) -> str:
+        args = []
+        for arg in (self.method_args[:-1] if self.method_args_virtual else self.method_args):
+            arg_str = str(Parameter(arg.name, kind=arg.kind))
+            if arg.default is not Parameter.empty:
+                arg_str += f" = DEFAULTS['{arg.name}']"
+            args.append(arg_str)
+        if self.method_args_virtual:
+            for arg in self.method_args_virtual:
+                args.append(str(Parameter(arg.name, kind=arg.kind)) + (" = UNSPECIFIED" if arg.default is not Parameter.empty else ""))
+        return f"""({", ".join(args)})"""
+
     @property
     def _docstring(self) -> str:
         """
diff --git a/tests/test_spec_class.py b/tests/test_spec_class.py
index e39e43a..bfc24db 100644
--- a/tests/test_spec_class.py
+++ b/tests/test_spec_class.py
@@ -754,7 +754,7 @@ class Spec:
         with pytest.raises(
             TypeError,
             match=re.escape(
-                "__init__() got unexpected keyword arguments: {'hidden_attr'}."
+                "__init__() got an unexpected keyword argument 'hidden_attr'"
             ),
         ):
             Spec(hidden_attr="Not here")