code: public Queue<PoolGroupSchedulable> getPreemptQueue() {
      if (preemptQueue == null) {
        preemptQueue = createPoolGroupQueue(ScheduleComparator.FAIR_PREEMPT);
      }
      return preemptQueue;
    }
docs: Get the queue of the pool groups sorted for preemption
  @return the queue of pool sorted for preemption