final protected function getCss($data_only = false)
    {
        $files = $this->page->css->getFiles();

        if ($data_only) {
            return $files;
        }

        $html = '';

        // Start reading
        foreach ($files as $file) {
            $html .= PHP_EOL . '<link rel="stylesheet" type="text/css" href="' . $file . '">';
        }

        return $html;
    }