docs: def _format_unhashed_feature(feature, weight, hl_spaces):
      # type: (...) -> str
      """ Format unhashed feature: show first (most probable) candidate,
      display other candidates in title attribute.
      """
      if not feature:
          return ''
      else:
          first, rest = feature[0], feature[1:]
          html = format_signed(
              first, lambda x: _format_single_feature(x, weight, hl_spaces))
          if rest:
              html += ' <span title="{}">&hellip;</span>'.format(
                  '\n'.join(html_escape(format_signed(f)) for f in rest))
          return html