RestoreObjectsCallback callback) {
  if (saved_object_graph().nodes_size() == 0 ||
      trackable_object_graph().nodes_size() == 0) {
    return absl::OkStatus();
  }

  // Start from root nodes of both the SavedObjectGraph and TrackableObjectGraph
  // and descend to leaves. Note that the TrackableObjectGraph can have cycles
  // (as can the SavedObjectGraph).
  // This is detected and cycle edges are skipped.

  SavedModelV2Bundle bundle;
  TF_ASSERT_OK(SavedModelV2Bundle::Load(export_dir, &bundle));

  // Ensure that there are nodes in the trackable_object_graph.
  EXPECT_GT(bundle.trackable_object_graph().nodes_size(), 0);

  RestoreVarsAndVerify(&bundle, {"variable_x", "variable_y", "child_variable"});
}

TEST_F(BundleV2Test, LoadsCyclicModule) {
  const std::string export_dir =

// The string key becomes the "name" attribute of the SerializedTensor proto
// in the TrackableObjectGraph,
// https://github.com/tensorflow/tensorflow/blob/ddc1bbad3dfd4a089eb96014f26cc16664b1b2f8/tensorflow/core/protobuf/trackable_object_graph.proto#L26
// And the checkpoint_key is a globally unique string derived from this name:

  }

  if (!value_it->second.has_tensor()) {
    return nullptr;
  }

  return &value_it->second.tensor();
}

const TrackableObjectGraph::TrackableObject::SerializedTensor*
FindSerializedTensorInTrackable(
    const TrackableObjectGraph::TrackableObject& trackable_object,
    StringPiece name) {
  for (const auto& maybe_serialized_tensor : trackable_object.attributes()) {