protected function unmarshallChildrenKnown(DOMElement $element, QtiComponentCollection $children)
    {
        if (($numberRepeats = $this->getDOMElementAttributeAs($element, 'numberRepeats')) !== null) {

            if (Format::isInteger($numberRepeats)) {
                $numberRepeats = intval($numberRepeats);
            }

            $object = new Repeat($children, $numberRepeats);

            return $object;
        } else {
            $msg = "The mandatory attribute 'numberRepeats' is missing from element '" . $element->localName . "'.";
            throw new UnmarshallingException($msg, $element);
        }
    }