docs: public Future<?> scheduleWithFixedDelay(Runnable task, long initialDelay, long delay, TimeUnit unit)
      {
          Preconditions.checkState(isOpen.get(), "CloseableExecutorService is closed");
  
          ScheduledFuture<?> scheduledFuture = scheduledExecutorService.scheduleWithFixedDelay(task, initialDelay, delay, unit);
          return new InternalScheduledFutureTask(scheduledFuture);
      }