private function findNonExistingContentTypeGroupIdentifier()
    {
        $i = 0;
        while ($i++ < 20) {
            $identifier = 'ctg' . rand(10000, 99999);
            if (!$this->checkContentTypeGroupExistenceByIdentifier($identifier)) {
                return $identifier;
            }
        }

        throw new \Exception('Possible endless loop when attempting to find a new identifier to ContentTypeGroups');
    }