code: func ValidateHasLabel(meta metav1.ObjectMeta, fldPath *field.Path, key, expectedValue string) field.ErrorList {
  	allErrs := field.ErrorList{}
  	actualValue, found := meta.Labels[key]
  	if !found {
  		allErrs = append(allErrs, field.Required(fldPath.Child("labels").Key(key),
  			fmt.Sprintf("must be '%s'", expectedValue)))
  		return allErrs
  	}
  	if actualValue != expectedValue {
  		allErrs = append(allErrs, field.Invalid(fldPath.Child("labels").Key(key), meta.Labels,
  			fmt.Sprintf("must be '%s'", expectedValue)))
  	}
  	return allErrs
  }
docs: // ValidateHasLabel requires that metav1.ObjectMeta has a Label with key and expectedValue