// want to freeze (i.e. its name is contained in variable_node_names). If there
// is no such handle in the graph (or we do not want to save that variable)
// then NotFound error is returned.
StatusOr<string> GetHandleNameIfNeedsToFreeze(
    const std::unordered_map<string, NodeDef*>& name_to_node_map,
    string node_name, const std::unordered_set<string>& variable_node_names) {
  StatusOr<string> var_handle_name =