Is there a way to make an indeterminate checkbutton with PyGtk?

I am designing a GUI where I have a list of checkable items that also has a sublist of checkable items. I want to graphically represent in the parent checkbox if only some of the child items are checked. I have been searching Google for hours with this and the only documents explain how to style a possible button. Is there a way in Gtk to do this cleanly?