/**
  * @return form_RecipientGroupListService
  */
 public static function getInstance()
 {
     if (self::$instance === null) {
         self::$instance = self::getServiceClassInstance(get_class());
     }
     return self::$instance;
 }
 /**
  * @return form_persistentdocument_recipientGroupList
  */
 protected function initPersistentDocument()
 {
     return form_RecipientGroupListService::getInstance()->getNewDocumentInstance();
 }