message: List the save/restore nodes in the set of nodes to preserve
diff: @@ -76,6 +76,16 @@ std::unordered_set<string> GrapplerItem::NodesToPreserve() const {
  for (const auto& node : init_ops) {
  result.insert(NodeName(node));
  }
  + if (!save_op.empty()) {
  + result.insert(NodeName(save_op));
  + }
  + if (!restore_op.empty()) {
  + result.insert(NodeName(restore_op));
  + }
  + if (!save_restore_loc_tensor.empty()) {
  + result.insert(NodeName(save_restore_loc_tensor));
  + }
  +
  for (const auto& queue_runner : queue_runners) {
  for (const string& enqueue_op : queue_runner.enqueue_op_name()) {
  result.insert(NodeName(enqueue_op));
  