docs: public void startPurge(WakeableLooper wakeableLooper) {
      synchronized (CacheCore.class) {
        if (looper == null) {
          looper = wakeableLooper;
        }
  
        looper.registerTimerEvent(interval, new Runnable() {
          @Override
          public void run() {
            purge();
          }
        });
      }
    }