TF_Output inputs[2];
    TF_Output outputs[1];
    TF_Output grad_outputs[2];

    BuildSuccessGraph(inputs, outputs);

    AddGradients(false, prefix1, inputs, 2, outputs, 1, grad_outputs);
    if (prefix2 != nullptr) {
      AddGradients(false, prefix2, inputs, 2, outputs, 1, grad_outputs);
    }
  }

  TF_Status* s_;
  TF_Graph* graph_;
  TF_Graph* expected_graph_;
};