code: public Observable<Long> getTickObservable(int interval, int total, boolean intermediate) {
          return Observable.intervalRange(0, total, intermediate ? 0 : interval, interval, TimeUnit.SECONDS);
      }
docs: return tick observable for each user, user should handle the observable with cell's lifecycle
  @param interval timer interval, in TimeUnit.SECOND
  @param total total event count
  @param intermediate true, get event immediately
  @return
  @since 3.0.0