fadeOut difference in execution due to version difference

I am trying to transition my character’s animation from one to another but having trouble due to version difference I think. I am watching @wawasensei portfolio video and the fadeOut method in the return doesn’t works cuz it’s getting an undefined object oriented something i don’t know can someone help please. Everything works fine but the fadeOut effect is not working so when I change animation it goes to T pose in an instance and then fadeIn to the new chosen animation.