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.

  const SavedObjectGraph& saved_object_graph() {
    return meta_graph_def().object_graph_def();
  }

  /// TrackableObjectGraph loaded from the variable_reader() checkpoint.
  TrackableObjectGraph& trackable_object_graph() {
    return trackable_object_graph_;
  }

  /// BundleReader for accessing the variables bundle.
  BundleReader* variable_reader() { return variable_reader_.get(); }

  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:

  // Returns the path to the variables file.
  const std::string GetVariablesFilepath() const { return variables_filepath_; }

 private:
  SavedModel saved_model_proto_;
  TrackableObjectGraph trackable_object_graph_;
  std::unique_ptr<tensorflow::BundleReader> variable_reader_;
  std::string variables_filepath_;
  bool has_checkpoint_;
  absl::flat_hash_map<std::string, const NodeDef*> graph_def_nodes_by_name_;
};

#include "tensorflow/core/framework/types.pb.h"
#include "tensorflow/core/protobuf/saved_object_graph.pb.h"
#include "tensorflow/core/protobuf/struct.pb.h"
#include "tensorflow/core/protobuf/trackable_object_graph.pb.h"

namespace tf {
namespace libtf {
namespace runtime {

using tensorflow::AbstractContext;
using tensorflow::AbstractFunctionPtr;
using tensorflow::DataType;
using tensorflow::FunctionDef;

#include "tensorflow/core/platform/stringpiece.h"
#include "tensorflow/core/protobuf/saved_object_graph.pb.h"
#include "tensorflow/core/protobuf/struct.pb.h"
#include "tensorflow/core/protobuf/trackable_object_graph.pb.h"

namespace tensorflow {
namespace internal {
namespace {

using StructuredValueDictEntry =
    protobuf::MapPair<std::string, StructuredValue>;

  return tf_package;
}

tensorflow::StatusOr<std::string> TFPackage::GetVariableCheckpointKey(
    int index) {
  // TODO(danielellis): make sure valid index
  const auto& trackable_object = trackable_object_graph_.nodes(index);
  const TrackableObjectGraph::TrackableObject::SerializedTensor*
      serialized_tensor = nullptr;
  for (auto& maybe_serialized_tensor : trackable_object.attributes()) {

  }

  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()) {