int GetResultIndexForEdge(const Edge* edge) const;

    // Creates an _Arg node for the src node of edge, and add its index to
    // args_by_src_, if none exists yet. Also adds its index to args_by_dst_,
    // and adds the edge within the subgraph from the _Arg node to the image of
    // the dst node.
    Status RecordArg(const Edge* edge,
                     const absl::flat_hash_map<const Node*, Node*>& node_images,