code: func ValidateStatefulSetStatusUpdate(statefulSet, oldStatefulSet *apps.StatefulSet) field.ErrorList {
  	allErrs := field.ErrorList{}
  	allErrs = append(allErrs, ValidateStatefulSetStatus(&statefulSet.Status, field.NewPath("status"))...)
  	allErrs = append(allErrs, apivalidation.ValidateObjectMetaUpdate(&statefulSet.ObjectMeta, &oldStatefulSet.ObjectMeta, field.NewPath("metadata"))...)
  	// TODO: Validate status.
  	if apivalidation.IsDecremented(statefulSet.Status.CollisionCount, oldStatefulSet.Status.CollisionCount) {
  		value := int32(0)
  		if statefulSet.Status.CollisionCount != nil {
  			value = *statefulSet.Status.CollisionCount
  		}
  		allErrs = append(allErrs, field.Invalid(field.NewPath("status").Child("collisionCount"), value, "cannot be decremented"))
  	}
  	return allErrs
  }
docs: // ValidateStatefulSetStatusUpdate tests if required fields in the StatefulSet are set.