code: func newKVOrNil(conf jsonconfig.Obj) (sorted.KeyValue, error) {
  	if len(conf) == 0 {
  		return nil, nil
  	}
  	return sorted.NewKeyValueMaybeWipe(conf)
  }
docs: // newKVOrNil wraps sorted.NewKeyValue and adds the ability
  // to pass a nil conf to get a (nil, nil) response.