code: func ConvertDownwardAPIFieldLabel(version, label, value string) (string, string, error) {
  	if version != "v1" {
  		return "", "", fmt.Errorf("unsupported pod version: %s", version)
  	}
  
  	if path, _, ok := fieldpath.SplitMaybeSubscriptedPath(label); ok {
  		switch path {
  		case "metadata.annotations", "metadata.labels":
  			return label, value, nil
  		default:
  			return "", "", fmt.Errorf("field label does not support subscript: %s", label)
  		}
  	}
  
  	switch label {
  	case "metadata.annotations",
  		"metadata.labels",
  		"metadata.name",
  		"metadata.namespace",
  		"metadata.uid",
  		"spec.nodeName",
  		"spec.restartPolicy",
  		"spec.serviceAccountName",
  		"spec.schedulerName",
  		"status.phase",
  		"status.hostIP",
  		"status.podIP":
  		return label, value, nil
  	// This is for backwards compatibility with old v1 clients which send spec.host
  	case "spec.host":
  		return "spec.nodeName", value, nil
  	default:
  		return "", "", fmt.Errorf("field label not supported: %s", label)
  	}
  }
docs: // ConvertDownwardAPIFieldLabel converts the specified downward API field label
  // and its value in the pod of the specified version to the internal version,
  // and returns the converted label and value. This function returns an error if
  // the conversion fails.