code: func newDelRangeManager(store kv.Storage, sessPool *sessionPool) delRangeManager {
  	dr := &delRange{
  		store:        store,
  		sessPool:     sessPool,
  		storeSupport: store.SupportDeleteRange(),
  		quitCh:       make(chan struct{}),
  	}
  	if !dr.storeSupport {
  		dr.emulatorCh = make(chan struct{}, delBackLog)
  		dr.keys = make([]kv.Key, 0, delBatchSize)
  	}
  	return dr
  }
docs: // newDelRangeManager returns a delRangeManager.