How does Angular Bootstrap $modal animate out?

Question

I'm not using any bootstrap styles. I'm customizing everything completely. It's fairly straight forward to animate in, because the $modal uses .fade.in. I was able to override those styles and it works great. But how does the modal animate out? I see no classes being applied or removed. It is simply removed from the DOM instantly.

How can I customize the animate out event? Does it use CSS classes? Does it use JS?

It seems this question is very similar: https://stackoverflow.com/questions/20595622/how-to-slideout-a-bootstrap-modal-in-angular. Unfortunately there is not a solution.