code: public void shutdown(Duration quietPeriod, Duration timeout) {
          shutdown(quietPeriod.toNanos(), timeout.toNanos(), TimeUnit.NANOSECONDS);
      }
docs: Shutdown this client and close all open connections. The client should be discarded after calling shutdown.
  
  @param quietPeriod the quiet period as described in the documentation
  @param timeout the maximum amount of time to wait until the executor is shutdown regardless if a task was submitted
  during the quiet period
  @since 5.0