code: func (pdb *BrokerWatcher) Watch(resp func(keyval.BytesWatchResp), closeChan chan string, keys ...string) error {
  	var prefixedKeys []string
  	for _, key := range keys {
  		prefixedKeys = append(prefixedKeys, pdb.prefixKey(key))
  	}
  	return pdb.Client.Watch(func(origResp keyval.BytesWatchResp) {
  		r := origResp.(*watchResp)
  		r.key = strings.TrimPrefix(r.key, pdb.prefix)
  		resp(r)
  	}, closeChan, prefixedKeys...)
  }
docs: // Watch starts subscription for changes associated with the selected <keys>.
  // KeyPrefix defined in constructor is prepended to all <keys> in the argument
  // list. The prefix is removed from the keys returned in watch events.
  // Watch events will be delivered to <resp> callback.