///
  /// Similar to `rename_file`, but both `src` and `dst` exist after this call
  /// with the same contents. In case of error, both `src` and `dst` keep the
  /// same state as before the call.
  ///
  /// If `dst` is a directory, creates a file with the same name as the source
  /// inside the target directory.
  ///
  /// Plugins:
  ///   * Must set `status` to `TF_OK` if rename was completed.

  // be executed as an op. Return error if the function with the same name
  // already exists.
  virtual Status AddFunctionDef(const FunctionDef& fdef) = 0;

  // Notifies about the function removal.
  virtual Status AddRemoveFunctionNotifier(const string& func,
                                           std::function<void()> notifier) = 0;

  // Same as `AddFunctionDef`, but additionally saves the `stack_traces` under