// size of `callee_ref_nodes` but for now we don't ceare.
    if (!callee_ref_nodes.empty()) {
      return true;
    }
  }

  return false;
}

// Helper for GetNodesRelatedToRefVariables that traverses the graph in one
// direction.
Status GetNodesRelatedToRefVariablesInDirection(
    const Graph& graph, FunctionLibraryRuntime* lib_runtime,

//
// We assume each node has a trivial path to itself so the returned set includes
// all of the nodes that have ref variables as input or output.
absl::StatusOr<absl::flat_hash_set<Node*>> GetNodesRelatedToRefVariables(
    const Graph& graph, FunctionLibraryRuntime* lib_runtime);

// Deterministically serialized the graph to a byte string.
absl::StatusOr<std::string> SerializeGraphDeterministic(const Graph& graph);

  FunctionLibraryRuntime* lib_runtime =
      pflr->GetFLR(ProcessFunctionLibraryRuntime::kDefaultFLRDevice);

  TF_ASSIGN_OR_RETURN(absl::flat_hash_set<Node*> nodes_related_to_ref_vars,
                      GetNodesRelatedToRefVariables(*graph, lib_runtime));

  std::vector<string> names;
  absl::c_transform(nodes_related_to_ref_vars, std::back_inserter(names),
                    [](Node* n) { return n->name(); });
  absl::c_sort(names);

                    options.flib_def);
  }

  *options.graph = std::move(graph_out);

  TF_ASSIGN_OR_RETURN(absl::flat_hash_set<Node*> ref_related_nodes,
                      GetNodesRelatedToRefVariables(**options.graph, flr));
  for (Node* node : (*options.graph)->nodes()) {
    bool has_ref_vars = ref_related_nodes.contains(node);
    node->AddAttr(kXlaHasReferenceVarsAttr, has_ref_vars);