public function toString(array $opts = array())
    {
        $eol = empty($opts['canonical'])
            ? $this->_eol
            : "\r\n";
        $text = '';

        foreach ($this->toArray($opts) as $key => $val) {
            foreach ((is_array($val) ? $val : array($val)) as $entry) {
                $text .= $key . ': ' . $entry . $eol;
            }
        }

        return $text . $eol;
    }