Ng-enter didn't applicate on my items

Hi to everyone, i’m new at Ionic. I’m trying to implement some nice animation in my app. I followed this guide:

but when i tried the part with the ng-enter class and the stagger, it doesn’t work. If i don’t use the ng-enter, all animation work great. My code is the same of the example. I really don’t know why that happen!

No one can help me? I need it to create very beautiful animation…

Same thing is happening to me. ngEnter doesn’t seem to be added to my ion-items.