protected function determineFormatVersion(\XMLReader $xmlReader)
    {
        while ($xmlReader->nodeType !== \XMLReader::ELEMENT || $xmlReader->name !== 'nodes') {
            if (!$xmlReader->read()) {
                break;
            }
        }

        if ($xmlReader->name === 'nodes' && $xmlReader->nodeType === \XMLReader::ELEMENT) {
            return $xmlReader->getAttribute('formatVersion');
        }

        return false;
    }