const ParallelDevice& device_;
  std::vector<TensorHandlePtr> tensors_;
  // Parallel tensors are immutable but compute their shape lazily unless it is
  // provided on construction. The optional has a value if the lazy computation
  // has been completed or the shape was provided on construction.
  mutable absl::optional<std::vector<int64_t>> shape_;
  const TF_DataType dtype_;
};

template <typename DataType>

};

struct TF_DeprecatedSession {
  tensorflow::Session* session;
};

struct TF_Library {
  void* lib_handle;
  TF_Buffer op_list;
};

struct TF_Graph {
  TF_Graph();

  mutable tensorflow::mutex mu;
  tensorflow::Graph graph TF_GUARDED_BY(mu);

  // Runs shape inference.
  tensorflow::ShapeRefiner refiner TF_GUARDED_BY(mu);

  // Maps from name of an operation to the Node* in 'graph'.

// In either case, it deletes `desc`.
TF_CAPI_EXPORT extern TF_Operation* TF_FinishOperation(
    TF_OperationDescription* desc, TF_Status* status);

// TF_Operation functions.  Operations are immutable once created, so
// these are all query functions.

TF_CAPI_EXPORT extern const char* TF_OperationName(TF_Operation* oper);
TF_CAPI_EXPORT extern const char* TF_OperationOpType(TF_Operation* oper);

  void Run(TF_Status* s);

  void CloseAndDelete(TF_Status* s);

  TF_Tensor* output_tensor(int i) { return output_values_[i]; }

  TF_Session* mutable_session() { return session_; }

 private:
  void DeleteInputValues();
  void ResetOutputValues();

  TF_Session* session_;
  std::vector<TF_Output> inputs_;
  std::vector<TF_Tensor*> input_values_;

  /// Notification for stopping the cache pruning thread.
  absl::Notification stop_pruning_thread_;

  /// Guards access to the block map, LRU list, and cached byte count.
  mutable absl::Mutex mu_;

  /// The block map (map from Key to Block).
  BlockMap block_map_ ABSL_GUARDED_BY(mu_);

  /// The LRU list of block keys. The front of the list identifies the most
  /// recently accessed block.