[WIP] Adds some checks to variable elimination to give more meaningful errors

pgmpy/inference/ExactInference.py

@@ -64,6 +64,19 @@ def _get_elimination_order(self, variables, evidence, elimination_order):
         -------
         list: A list of variables names in the order they need to be eliminated.
         """
+        for var in variables:
+            if var not in self.model.nodes():
+                raise ValueError(
+                    "The variable: {var} is not in the model".format(var=var)
+                )
+
+        if evidence is not None:
+            for var, state in evidence.items():
+                if var not in self.model.nodes():
+                    raise ValueError(
+                        "The variable: {var} is not in the model".format(var=var)
+                    )
+
         to_eliminate = (
             set(self.variables)
             - set(variables)

pgmpy/tests/test_inference/test_ExactInference.py

@@ -188,6 +188,21 @@ def test_induced_width(self):
         )
         self.assertEqual(2, result_width)
 
+    def test_query_unknown_var(self):
+        self.assertRaises(
+            ValueError, self.bayesian_inference.query, {"variables": ["Unknown"]}
+        )
+        self.assertRaises(
+            ValueError,
+            self.bayesian_inference.query,
+            {"variables": ["J"], "evidence": {"Unknown": 1}},
+        )
+        self.assertRaises(
+            ValueError,
+            self.bayesian_inference.query,
+            {"variables": ["Unknown"], "evidence": {"Unknown": 1}},
+        )
+
     def tearDown(self):
         del self.bayesian_inference
         del self.bayesian_model