docs: public void addPoller(PollRunnable task, long delay, TimeUnit timeUnit) {
      ScheduledExecutorService service = executor.get();
      if (service != null) {
        service.scheduleWithFixedDelay(task, 0, delay, timeUnit);
      } else {
        throw new IllegalStateException(
            "you must start the scheduler before tasks can be submitted");
      }
    }