code: func (s *Serializer) RecognizesData(peek io.Reader) (bool, error) {
  	_, ok := utilyaml.GuessJSONStream(peek, 2048)
  	if s.yaml {
  		return !ok, nil
  	}
  	return ok, nil
  }
docs: // RecognizesData implements the RecognizingDecoder interface.