bool IsPersistent() const { return persistent_; }

 private:
  TensorTape tensor_tape_;
  OpTape<BackwardFunction, TapeTensor> op_tape_;
  int64_t next_op_id_{0};

  // Map from tensor id to number of remaining usages (i.e. how many entries in
  // the tape refer to it); to aid in tape garbage collection.
  std::unordered_map<int64_t, int64_t> tensor_usage_;

//      params->device_type = "MY_DEVICE";
//
//      // Disable certain optimizer.
//      params->optimizer_configs->struct_size =
//      TP_OPTIMIZER_CONFIGS_STRUCT_SIZE; params->optimizer_configs->remapping =
//      TF_TriState_Off;
//
//      // Set functions to create a new optimizer.
//      params->optimizer->struct_size = TP_OPTIMIZER_STRUCT_SIZE;
//      params->optimizer->create_func = (My_optimizer::create_func);