如何从collection_select rails处理数组

I have a form that uses collection_select to be able to select multiple groups. But when I try to create a new record it fails in my notifications_controller.rb. The parameters are being passed correctly I think it might have to do with collection_select being passed as an array. I just can't for the life of me figure out how to handle it in the controller. I have a form that uses collection_select to be