docs: public Map<String, Serializable> getState() {
      Map<String, Serializable> ret = new HashMap<>();
      // get potential eviction policy state
      if (evictionPolicy.getState() != null) {
        ret.put(EVICTION_STATE_KEY, (Serializable) evictionPolicy.getState());
      }
      // get potential trigger policy state
      if (triggerPolicy.getState() != null) {
        ret.put(TRIGGER_STATE_KEY, (Serializable) triggerPolicy.getState());
      }
      ret.put(QUEUE, (Serializable) this.queue);
      ret.put(EXPIRED_EVENTS, (Serializable) this.expiredEvents);
      ret.put(PRE_WINDOW_EVENTS, (Serializable) this.prevWindowEvents);
      ret.put(EVENTS_SINCE_LAST_EXPIRY, this.eventsSinceLastExpiry.get());
      return ret;
    }