public function __construct($relationModel)
 {
     $metadata = Activity::getMetadata();
     assert('in_array(get_class($relationModel), $metadata["Activity"]["activityItemsModelClassNames"])');
     parent::__construct($relationModel);
 }
 public function __construct($relationModel)
 {
     $metadata = Conversation::getMetadata();
     assert('in_array(get_class($relationModel), $metadata["Conversation"]["conversationItemsModelClassNames"])');
     parent::__construct($relationModel);
 }