code: func (persistentvolumeclaimStatusStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) {
  	newPv := obj.(*api.PersistentVolumeClaim)
  	oldPv := old.(*api.PersistentVolumeClaim)
  	newPv.Spec = oldPv.Spec
  	if !utilfeature.DefaultFeatureGate.Enabled(features.ExpandPersistentVolumes) && oldPv.Status.Conditions == nil {
  		newPv.Status.Conditions = nil
  	}
  }
docs: // PrepareForUpdate sets the Spec field which is not allowed to be changed when updating a PV's Status