};

struct TF_OperationDescription {
  TF_OperationDescription(TF_Graph* g, const char* op_type,
                          const char* node_name)
      : node_builder(node_name, op_type, g->graph.op_registry()), graph(g) {}

  tensorflow::NodeBuilder node_builder;
  TF_Graph* graph;
  std::set<std::string> colocation_constraints;
};

struct TF_Operation {
  tensorflow::Node node;

 private:

  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));
  std::string expected_serialized;
  expected_op_def->SerializeToString(&expected_serialized);
  std::string actual_string(reinterpret_cast<const char*>(buffer->data),