TF_OperationDescription* desc = TF_NewOperation(graph, "AddN", name);
  TF_Output add_inputs[2] = {{l, 0}, {r, 0}};
  TF_AddInputList(desc, add_inputs, 2);
  TF_AddControlInput(desc, ctrl_op);
  return TF_FinishOperation(desc, s);
}

// If `op_device` is non-empty, set the created op on that device.
void BinaryOpHelper(const char* op_name, TF_Operation* l, TF_Operation* r,