TF_Buffer* buffer = TF_NewBuffer();

  TF_GraphGetOpDef(graph, "Add", buffer, status);
  ASSERT_EQ(TF_OK, TF_GetCode(status));
  const OpDef* expected_op_def;
  TF_ASSERT_OK(OpRegistry::Global()->LookUpOpDef("Add", &expected_op_def));
  string expected_serialized;
  expected_op_def->SerializeToString(&expected_serialized);
  string actual_string(reinterpret_cast<const char*>(buffer->data),