// We use ReverseDFS() to copy nodes. Make sure all nodes are reverse
    // reachable from sink node so all nodes will be copied.
    // TODO(b/77601805): consolidate copy graph functions.
    FixupSourceAndSinkEdges(host_fbody->graph);

    std::map<const Node*, Node*> node_map;
    node_map[host_fbody->graph->source_node()] = (*host_graph)->source_node();

    }
  }

  // Since we might have inserted and removed nodes from the graph, fix
  // source/sink edges and reconstruct the RPO ordering of nodes
  FixupSourceAndSinkEdges(graph_.get());

  // Prune nodes in the graph that are not reachable from the output.
  if (specs_.prune_unused_nodes) {
    std::unordered_set<const Node*> prune_start;