docs: public Future<?> submit(Runnable task)
      {
          Preconditions.checkState(isOpen.get(), "CloseableExecutorService is closed");
  
          InternalFutureTask<Void> futureTask = new InternalFutureTask<Void>(new FutureTask<Void>(task, null));
          executorService.execute(futureTask);
          return futureTask;
      }