public function setRecurrenceEventId($entity = null): string
    {
        $start = $entity instanceof EntityInterface ? $entity->get('start_date') : $entity['start_date'];
        $end = $entity instanceof EntityInterface ? $entity->get('end_date') : $entity['end_date'];
        $id = $entity instanceof EntityInterface ? $entity->get('id') : $entity['id'];

        $result = sprintf("%s__%s_%s", $id, strtotime($start), strtotime($end));

        return $result;
    }