private function getCssFromAllStyleNodes(\DOMXPath $xPath)
    {
        $styleNodes = $xPath->query('//style');

        if ($styleNodes === false) {
            return '';
        }

        $css = '';
        /** @var \DOMNode $styleNode */
        foreach ($styleNodes as $styleNode) {
            $css .= "\n\n" . $styleNode->nodeValue;
            $styleNode->parentNode->removeChild($styleNode);
        }

        return $css;
    }