protected function generateTheme()
    {
        $nodes = $this->xpath->query('/x:webspace/x:theme/x:key');
        if ($nodes->length > 0) {
            return $nodes->item(0)->nodeValue;
        }

        $nodes = $this->xpath->query('/x:webspace/x:theme');
        if (0 === $nodes->length) {
            return;
        }

        return $nodes->item(0)->nodeValue;
    }