Just taken a look at the controller, and yep...no function called that (it's off in the ips.ui.rating module) so that will be why it's not working. Mixin is for controllers.
No idea what you are trying to do before the function, but as it is called in the init of ips.ui.rating then wouldn't before initialize meet the same need? (unless you need something that the init is providing? Again...no idea what you are trying to do)