code: public EngineBuilder setTimerScheduler(final ScheduledExecutorService timerScheduler) {
      ArgumentUtil.requireNotNull(timerScheduler, "timerScheduler");
      setTimerScheduler(adaptTimerScheduler(timerScheduler));
      return this;
    }
docs: Sets the timer scheduler for the engine.
  <p>
  The lifecycle of the scheduler is not managed by the engine.
  
  @param timerScheduler the scheduler to use for the engine
  @return this builder