[Zope] Make a Python Products Add list show only certain meta types?

I have a custom Python class (Container) which uses Folder as it's base class. I also have a custom Python class (AnObject). I want it so that when you view a Container object, "AnObject" will be the only meta_type available to be added in the Add List. The problem is that since Container inherits from Folder, the Add List makes all object types available to be added. Is there any way to tell a class to show only certain meta_types? Kevin