///
  /// This call should block until filesystem confirms that all buffers have
  /// been flushed and persisted.
  ///
  /// DEFAULT IMPLEMENTATION: No op.
  void (*sync)(const TF_WritableFile* file, TF_Status* status);

  /// Closes `*file`.
  ///
  /// Flushes all buffers and deallocates all resources.
  ///
  /// Calling `close` must not result in calling `cleanup`.
  ///