code: func (pdb *BrokerWatcher) ListKeys(prefix string) (keyval.BytesKeyIterator, error) {
  	keys, qm, err := pdb.client.KV().Keys(pdb.prefixKey(prefix), "", nil)
  	if err != nil {
  		return nil, err
  	}
  
  	return &bytesKeyIterator{len: len(keys), keys: keys, prefix: pdb.prefix, lastIndex: qm.LastIndex}, nil
  }
docs: // ListKeys calls 'ListKeys' function of the underlying BytesConnectionEtcd.
  // KeyPrefix defined in constructor is prepended to the argument.