code: func (s *Serializer) RecognizesData(peek io.Reader) (ok, unknown bool, err error) {
  	if s.options.Yaml {
  		// we could potentially look for '---'
  		return false, true, nil
  	}
  	_, _, ok = utilyaml.GuessJSONStream(peek, 2048)
  	return ok, false, nil
  }
docs: // RecognizesData implements the RecognizingDecoder interface.