How to deal with menupath in dia.register_callback()

[Bao Niu <niubao56 gmail com>]

I tried this in my code:
dia.register_callback("ModKeys", "<Display>/Database/ModKeys", mod_keys())

I was expecting that there would be a new menu called "Database" showing up in the top, but instead it is "ModKeys=>Activate", what is the logic of menupath here?

I couldn't find documentation on this topic in our forum. Could anybody please help explain a bit? Many thanks.