protected function parseEntry($entry)
    {
        if (!get_property($entry, 'url')) {
            throw new \InvalidArgumentException('Url is missing or not accessible.');
        }
        $url        = get_property($entry, 'url');
        $lastmod    = get_property($entry, 'lastmod');
        $changefreq = get_property($entry, 'changefreq');
        $priority   = get_property($entry, 'priority');

        return [$url, $lastmod, $changefreq, $priority];
    }