public function visit(Aggregator $a)
{
if (!$a instanceof \lukaszmakuch\Aggregator\LabelGenerator\WithCustomLabel) {
throw new \lukaszmakuch\Aggregator\XmlPresenter\Exception\UnableToCreateXml();
}
$xmlDoc = new \DOMDocument();
$xmlDoc->loadXML($a->getActualAggregator()->accept($this->presenterOfEveryAggregator));
$xmlDoc->documentElement->setAttribute("label", $a->getLabel());
return $xmlDoc->saveXML();
}
