if controllers.IsNil(item) {
			// This should be extremely rare, maybe impossible due to the mutex.
			continue
		}
		res = append(res, item)
	}
	return res
}

// CreateIndexWithDelegate creates a simple index, keyed by key K, over an informer for O. This is similar to
// Informer.AddIndex, but is easier to use and can be added after an informer has already started.

	}))
	p.webhooks = kclient.NewFiltered[*admissionregistrationv1.MutatingWebhookConfiguration](client, kubetypes.Filter{
		ObjectFilter: kubetypes.NewStaticObjectFilter(isTagWebhook),
	})
	p.index = kclient.CreateIndexWithDelegate[string, *admissionregistrationv1.MutatingWebhookConfiguration](p.webhooks,
		func(o *admissionregistrationv1.MutatingWebhookConfiguration) []string {
			rev := o.GetLabels()[label.IoIstioRev.Name]
			if rev == "" {

func TestIndexDelegate(t *testing.T) {
	c := kube.NewFakeClient()
	pods := New[*corev1.Pod](c)
	c.RunAndWait(test.NewStop(t))
	var index *Index[string, *corev1.Pod]
	adds := atomic.NewInt32(0)
	index = CreateIndexWithDelegate[string, *corev1.Pod](pods, func(pod *corev1.Pod) []string {
		return []string{pod.Spec.ServiceAccountName}
	}, controllers.EventHandler[*corev1.Pod]{
		AddFunc: func(obj *corev1.Pod) {