code: private function longestFlag($flag_sets)
      {
          $longest = 0;
          foreach ($flag_sets as $flags) {
              foreach ($flags as $flag) {
                  $longest = max($longest, strlen($this->renderFlag($flag)));
              }
          }
  
          return $longest;
      }
docs: Works out the longest flag for formatting purposes.
  
  @param array $flag_sets The internal flag set list.