code: func (f *sharedInformerFactory) InformerFor(obj runtime.Object, newFunc internalinterfaces.NewInformerFunc) cache.SharedIndexInformer {
  	f.lock.Lock()
  	defer f.lock.Unlock()
  
  	informerType := reflect.TypeOf(obj)
  	informer, exists := f.informers[informerType]
  	if exists {
  		return informer
  	}
  
  	resyncPeriod, exists := f.customResync[informerType]
  	if !exists {
  		resyncPeriod = f.defaultResync
  	}
  
  	informer = newFunc(f.client, resyncPeriod)
  	f.informers[informerType] = informer
  
  	return informer
  }
docs: // InternalInformerFor returns the SharedIndexInformer for obj using an internal
  // client.