def METHOD_NAME(self):
    """Does the method convert dicts of dicts as expected?"""
    self._set_attributes(self.check_dictdict, {1:{1: [1,2,3], 2: [4,5,6]}, 2:{3:[7, 8, 9], 4:[10, 11, 12]}})
    self.data.listify()
    for attr in self.check_dictdict:
        for a in getattr(self.data, attr).values():
            for b in getattr(attr, a).values():
                assert isinstance(b, list)