code: func (itr *blocksItr) Close() {
  	itr.mgr.cpInfoCond.L.Lock()
  	defer itr.mgr.cpInfoCond.L.Unlock()
  	itr.closeMarkerLock.Lock()
  	defer itr.closeMarkerLock.Unlock()
  	itr.closeMarker = true
  	itr.mgr.cpInfoCond.Broadcast()
  	if itr.stream != nil {
  		itr.stream.close()
  	}
  }
docs: // Close releases any resources held by the iterator