code: func splitNodeKey(key []byte) (id ID, rest []byte) {
  	if !bytes.HasPrefix(key, []byte(dbNodePrefix)) {
  		return ID{}, nil
  	}
  	item := key[len(dbNodePrefix):]
  	copy(id[:], item[:len(id)])
  	return id, item[len(id)+1:]
  }
docs: // splitNodeKey returns the node ID of a key created by nodeKey.