code: func (persistentvolumeStatusStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) {
  	newPv := obj.(*api.PersistentVolume)
  	oldPv := old.(*api.PersistentVolume)
  	newPv.Spec = oldPv.Spec
  }
docs: // PrepareForUpdate sets the Spec field which is not allowed to be changed when updating a PV's Status