const Graph& graph, const std::vector<Node*>& sink_nodes,
    std::unique_ptr<Graph>* pruned_graph,
    absl::flat_hash_map<const Node*, Node*>* node_images,
    FunctionLibraryDefinition* library) {
  // First copy all ancestor nodes of sink_nodes into a new graph.
  pruned_graph->reset(new Graph(library));
  (*pruned_graph)->set_versions(graph.versions());
  ReverseDFSFrom(graph, sink_nodes,
                 /*enter=*/nullptr,