@Override
  void unlinked() {
    // we don't actually remove the parent link when this directory is unlinked, but the parent's
    // link count should go down all the same
    parent().decrementLinkCount();
  }
Returns the parent of this directory. If this directory has been deleted, this returns the
directory it was in when it was deleted.
jimfs/src/main/java/com/google/common/jimfs/Directory.java