public function toXML(DOMElement $parent) : DOMElement
    {
        $doc = $parent->ownerDocument;

        $e = $doc->createElementNS(EntityAttributes::NS, 'mdattr:EntityAttributes');
        $parent->appendChild($e);

        /** @var \SAML2\XML\saml\Attribute|\SAML2\XML\Chunk $child */
        foreach ($this->children as $child) {
            $child->toXML($e);
        }

        return $e;
    }