code: public SortedSet<NotificationsByObservable<?>> getNotificationsByObservable() {
          SortedSet<NotificationsByObservable<?>> notificationsByObservableSnapshot = new TreeSet<NotificationsByObservable<?>>();
          for (Entry<Subscriber<?>, Queue<SimpleContext<?>>> notificationsForObservable : notificationsByObservable.entrySet()) {
              notificationsByObservableSnapshot.add(new NotificationsByObservable(notificationsForObservable));
          }
          return notificationsByObservableSnapshot;
      }
docs: a copy sorted by time  of the all the state useful for analysis.
  @return