protected function visitLimitation(Generator $generator, Limitation $limitation)
    {
        $generator->startHashElement('limitation');

        $generator->startAttribute('identifier', $limitation->getIdentifier());
        $generator->endAttribute('identifier');

        $generator->startHashElement('values');
        $generator->startList('ref');

        foreach ($limitation->limitationValues as $limitationValue) {
            $generator->startObjectElement('ref');
            $generator->startAttribute('href', $limitationValue);
            $generator->endAttribute('href');
            $generator->endObjectElement('ref');
        }

        $generator->endList('ref');
        $generator->endHashElement('values');

        $generator->endHashElement('limitation');
    }