Python COM: Implementing someone else's interface

[Kent]

I'm trying to write a PalmDesktop Add-In in Python.  I get an error
when PalmDesktop tries to create an instance of my server class.  The
last few lines of the stack trace look like this:

    return pythoncom.WrapObject(self, reqIID)
pywintypes.com_error: (-2147467262, 'No such interface supported',
None, None)
pythoncom error: CPyFactory::CreateInstance failed to create instance.
(80004005)

I assume it's because Palm is trying to create an instance of
IDesktopAddin.  How can let the Pythoncom framework know that I am an
IDesktopAddin?

Kent