private function document($html)
{
$doc = new Document();
$doc->html($html);
// Remove the doctype (if it exists) so we can use Document::$firstChild
if ($doc->doctype instanceof \DOMDocumentType) {
$doc->removeChild($doc->doctype);
}
// Remove any leading ProcessingInstructions
if ($doc->firstChild instanceof \DOMProcessingInstruction) {
$doc->removeChild($doc->firstChild);
}
return $doc;
}