code: func (f *StreamNameFlag) UnmarshalJSON(data []byte) error {
  	s := ""
  	if err := json.Unmarshal(data, &s); err != nil {
  		return err
  	}
  	if err := types.StreamName(s).Validate(); err != nil {
  		return err
  	}
  	*f = StreamNameFlag(s)
  	return nil
  }
docs: // UnmarshalJSON implements json.Unmarshaler.