code: private function renderFlagSet($flags, $explanation, $tab_stop)
      {
          $flag = array_shift($flags);
          $text = str_pad($this->renderFlag($flag), $tab_stop, ' ') . $explanation . "\n";
          foreach ($flags as $flag) {
              $text .= '  ' . $this->renderFlag($flag) . "\n";
          }
  
          return $text;
      }
docs: Generates the text for a single flag and it's alternate flags.
  
  @returns string           Help text for that flag group.