inline constexpr char kSavedModelTrainOpSignatureKey[] =
    "__saved_model_train_op";

// Key in the TensorBundle for the object graph proto.
inline constexpr char kObjectGraphProtoKey[] = "_CHECKPOINTABLE_OBJECT_GRAPH";

// Filename for the FingerprintDef protocol buffer.
inline constexpr char kFingerprintFilenamePb[] = "fingerprint.pb";

}  // namespace tensorflow

        tensorflow::Env::Default(), tf_package.variables_filepath_);
    tensorflow::Tensor object_graph_tensor;
    TF_RETURN_IF_ERROR(tf_package.variable_reader_->Lookup(
        tensorflow::kObjectGraphProtoKey, &object_graph_tensor));
    const auto* object_graph_string =
        reinterpret_cast<const tensorflow::tstring*>(
            object_graph_tensor.tensor_data().data());

                                       TrackableObjectGraph* object_graph) {
  Tensor object_graph_tensor;
  TF_RETURN_WITH_CONTEXT_IF_ERROR(
      bundle_reader->Lookup(kObjectGraphProtoKey, &object_graph_tensor),
      "SavedModel checkpoint does not contain object graph.");
  if (object_graph_tensor.dtype() != DT_STRING ||
      object_graph_tensor.dims() != 0 ||