code: def default_sorter_factory(search, index):
      sort_arg_name = 'sort'
      urlfield = request.values.get(sort_arg_name, '', type=str)
      if not urlfield:
          has_query = request.values.get('q', type=six.text_type)
          urlfield = current_app.config['RECORDS_REST_DEFAULT_SORT'].get(
              index, {}).get('query' if has_query else 'noquery', '')
      key, asc = parse_sort_field(urlfield)
      sort_options = current_app.config['RECORDS_REST_SORT_OPTIONS'].get(
          index, {}).get(key)
      if sort_options is None:
          return (search, {})
      search = search.sort(
          *[eval_field(f, asc) for f in sort_options['fields']]
      )
      return (search, {sort_arg_name: urlfield})