Restricting stan tests to supported versions

Author: MichaelClerx

.github/workflows/unit-test-python-coverage.yml

@@ -39,6 +39,10 @@ jobs:
           python -m pip install --upgrade pip setuptools wheel
           python -m pip install .
 
+      - name: install stan
+        if: ${{ matrix.python-version >= '3.10' && matrix.python-version < '3.13' }}
+        run : python -m pip install .[stan]
+
       - name: run unit tests
         run: |
           python run-tests.py --unit