code: func (s *Scheme) ConvertFieldLabel(version, kind, label, value string) (string, string, error) {
  	if s.fieldLabelConversionFuncs[version] == nil {
  		return "", "", fmt.Errorf("No field label conversion function found for version: %s", version)
  	}
  	conversionFunc, ok := s.fieldLabelConversionFuncs[version][kind]
  	if !ok {
  		return "", "", fmt.Errorf("No field label conversion function found for version %s and kind %s", version, kind)
  	}
  	return conversionFunc(label, value)
  }
docs: // Converts the given field label and value for an kind field selector from
  // versioned representation to an unversioned one.