private function extractStyleSheet(Element $element){
        if($element instanceof StyleSheet){
            $href = $element->attr('href');
            $this->addAsset('css', $href);

            $parsedUrl = parse_url($href);
            if ($this->isDeepParsing() && array_key_exists('path', $parsedUrl) && !array_key_exists('host',
                    $parsedUrl)
            ) {
                $file = $this->directory->getFile($parsedUrl['path']);
                if ($file->exists()) {
                    $this->loadStyleSheetAsset($file->read());
                }
            }
        }
    }