fix the case : tensor output in parent graph ---> Identity --> graph output

Author: pengwa

tests/test_optimizers.py

@@ -208,7 +208,6 @@ def test_identity_output_as_multiple_graph_outputs(self):
         self.run_identity_compare(["Z1", "Z2"], {"X": np.random.randn(2, 3, 4, 5).astype(np.float32)},
                                   model_proto, remaining_identity_num=1)
 
-
     def test_identity_in_subgraph_non_graph_output(self):
         node1 = helper.make_node("Add", ["X", "X"], ["Y"], name="add")
 

tf2onnx/optimizer/identity_optimizer.py

@@ -73,6 +73,12 @@ def _handle_non_graph_output_identity(self, graph, identity):
     def _handle_graph_output_identity(self, graph, identity, graph_outputs):
         input_id = identity.input[0]
         input_node = identity.inputs[0]
+
+        if input_node.graph != graph:
+            # If input node is in parent graph, we don't handle it now
+            log.debug("input node in parent graph, skip")
+            return False
+
         if input_node.is_graph_input():
             # Identity between input and output should not be removed.
             log.debug("skip identity between input and output")