TF_ASSIGN_OR_RETURN(Node * arg_node, function_body.graph->AddNode(arg_def));
  return arg_node;
}

// Add _Retval node that matches newly added `arg_node` and connect `arg_node`
// to it.
Status AddMatchingRetvalNode(const FunctionBody& function_body,
                             const int arg_idx, const DataType& data_type,
                             Node* arg_node) {