docs: def parent_subfolders(self, ident, ann_id=None):
          '''An unordered generator of parent subfolders for ``ident``.
  
          ``ident`` can either be a ``content_id`` or a tuple of
          ``(content_id, subtopic_id)``.
  
          Parent subfolders are limited to the annotator id given.
  
          :param ident: identifier
          :type ident: ``str`` or ``(str, str)``
          :param str ann_id: Username
          :rtype: generator of ``(folder_id, subfolder_id)``
          '''
          ann_id = self._annotator(ann_id)
          cid, _ = normalize_ident(ident)
          for lab in self.label_store.directly_connected(ident):
              folder_cid = lab.other(cid)
              subfolder_sid = lab.subtopic_for(folder_cid)
              if not folder_cid.startswith('topic|'):
                  continue
              folder = self.unwrap_folder_content_id(folder_cid)
              subfolder = self.unwrap_subfolder_subtopic_id(subfolder_sid)
              if folder['annotator_id'] != ann_id:
                  continue
              yield (folder['folder_id'], subfolder)