///     `dst` is a directory or if either of them is invalid.
  ///   * Might use any other error value for `status` to signal other errors.
  ///
  /// DEFAULT IMPLEMENTATION: Reads from `src` and writes to `dst`. Needs
  /// `new_random_access_file` and `new_writable_file`.
  void (*copy_file)(const TF_Filesystem* filesystem, const char* src,
                    const char* dst, TF_Status* status);