protected function addCollectionNode(DOMElement $element, $value)
    {
        if ($element->childNodes->length === 0 && $element->attributes->length === 0) {
            $this->convertElement($element, $value);

            return;
        }

        $child = $this->document->createElement($element->tagName);
        $element->parentNode->appendChild($child);
        $this->convertElement($child, $value);
    }