N98\Magento\Command\Developer\Module\UpdateCommand::putConfigXml PHP Method

    protected function putConfigXml(SimpleXMLElement $configXml)
    {
        $outFile = $this->getOutFile();
        $xml = $configXml->asXML();
        if (false === $xml) {
            throw new RuntimeException(sprintf('Failed to get XML from config SimpleXMLElement'));
        }
        file_put_contents($outFile, $this->asPrettyXml($xml));
    }