code: func (podDisruptionBudgetStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) {
  	newPodDisruptionBudget := obj.(*policy.PodDisruptionBudget)
  	oldPodDisruptionBudget := old.(*policy.PodDisruptionBudget)
  	// Update is not allowed to set status
  	newPodDisruptionBudget.Status = oldPodDisruptionBudget.Status
  
  	// Any changes to the spec increment the generation number, any changes to the
  	// status should reflect the generation number of the corresponding object.
  	// See metav1.ObjectMeta description for more information on Generation.
  	if !apiequality.Semantic.DeepEqual(oldPodDisruptionBudget.Spec, newPodDisruptionBudget.Spec) {
  		newPodDisruptionBudget.Generation = oldPodDisruptionBudget.Generation + 1
  	}
  }
docs: // PrepareForUpdate clears fields that are not allowed to be set by end users on update.