fix: exlude self-cycles in newer NetworkX versions

Author: f-allian

causal_testing/specification/causal_dag.py

@@ -169,16 +169,14 @@ def check_iv_assumptions(self, treatment, outcome, instrument) -> bool:
             )
 
         # (iii) Instrument and outcome do not share causes
-        if any(
-            (
-                cause
-                for cause in self.graph.nodes
-                if len(list(nx.all_simple_paths(self.graph, source=cause, target=instrument))) > 0
-                and len(list(nx.all_simple_paths(self.graph, source=cause, target=outcome))) > 0
-            )
-        ):
-            raise ValueError(f"Instrument {instrument} and outcome {outcome} share common causes")
 
+        for cause in self.graph.nodes:
+            if cause not in (instrument, outcome):  # exclude self-cycles due to breaking changes in NetworkX > 3.2
+                instrument_paths = list(nx.all_simple_paths(self.graph, source=cause, target=instrument))
+                outcome_paths = list(nx.all_simple_paths(self.graph, source=cause, target=outcome))
+                if len(instrument_paths) > 0 and len(outcome_paths) > 0:
+                    print(cause, instrument, instrument_paths, outcome, outcome_paths)
+                    raise ValueError(f"Instrument {instrument} and outcome {outcome} share common causes")
         return True
 
     def add_edge(self, u_of_edge: Node, v_of_edge: Node, **attr):