Remove last vestiges of 'constraint' stuff

pytools/graph.py

@@ -549,8 +549,6 @@ def dfs(node: NodeT) -> None:
 # }}}
 
 
-# {{{ tag propagation graph processing
-
 def undirected_graph_from_edges(
         edges: Iterable[Tuple[NodeT, NodeT]],
     ) -> GraphT[NodeT]:
@@ -566,7 +564,7 @@ def undirected_graph_from_edges(
 
     for lhs, rhs in edges:
         if lhs == rhs:
-            raise TypeError("Found matching LHS and RHS in constraints,"
+            raise TypeError("Found loop in edges,"
                             f" LHS, RHS = {lhs}")
 
         undirected_graph.setdefault(lhs, set()).add(rhs)
@@ -577,8 +575,8 @@ def undirected_graph_from_edges(
 
 
 def get_reachable_nodes(
-    undirected_graph: GraphT[NodeT],
-    source_node: NodeT) -> FrozenSet[NodeT]:
+        undirected_graph: GraphT[NodeT],
+        source_node: NodeT) -> FrozenSet[NodeT]:
     """
     Returns a :class:`frozenset` of all nodes in *undirected_graph* that are
     reachable from *source_node*.
@@ -597,7 +595,5 @@ def get_reachable_nodes(
 
     return frozenset(nodes_visited)
 
-# }}}
-
 
 # vim: foldmethod=marker