Actually, HtmlDoc already lists all module members in the inspected
module (regardless of whether they are modules imported from outside or
submodules defined inline). You can try it with the updated pydocfodder:

>>> import pydoc
>>> from test import pydocfodder
>>> pydoc.writedoc(pydocfodder)
wrote test.pydocfodder.html

... and check that test.pydocfodder.html contains a reference to
test.pydocfodder.submodule.