Created a shipping plugin, shipping_options not being called.

I've created a shipping plugin that seems to work pretty well. However, I want it to connect with fedex in certain conditions.

Everything seems to be working, except my "shipping_options" method inside my plugin doesn't seem to get called when it should. I noticed in the comments that this method is for "For calculated shipping modules".

How do I set my plugin as a calculated shipping module so that this method is called?

Thanks!