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;
    }