Extensions: Unloading DLLs?

[Jonathan McLin]

I'm creating an extension to make available to my Python app some features
in a third-party DLL.   This means my initMyModule() function must make a
LoadLibrary() call to load this third-party dll.  If I unload my module, I
should unload the DLL.  I can't seem to find any documentation on an
extension interface call for unload events.  What happens when I delete my
module?  Is there a (hard to find documentation on) call for which I should
implement an API?