private void LoopRec(Notification notification, Action <Notification> self)
 {
     notification.Accept(_observer);
     if (notification.Kind != NotificationKind.OnNext)
     {
         return;
     }
     notification = notification.Acknowldge();
     if (notification == null || notification.Kind == null)
     {
         return;
     }
     self(notification);
 }