code: private function reverseFindLastUsefulContent(DocBlock $doc, $from)
      {
          for ($index = $from - 1; $index >= 0; --$index) {
              if ($doc->getLine($index)->containsUsefulContent()) {
                  return $index;
              }
          }
  
          return null;
      }
docs: @param DocBlock $doc
  @param int      $from
  
  @return null|int