public function extractContent($content)
    {
        $regex = '~^('
            . '---'                                  // $matches[1] start separator
            . "){1}[\r\n|\n]*(.*?)[\r\n|\n]+("       // $matches[2] front matter
            . '---'                                  // $matches[3] end separator
            . "){1}[\r\n|\n]*(.*)$~s";               // $matches[4] document content

        return preg_match($regex, $content, $matches) === 1 ? ltrim($matches[4]) : $content;
    }