def parent(self):
    return self.key().parent()
When flat is True, PageNumberPagination should work as in
dataset/ETHPy150Open CollabQ/CollabQ/.google_appengine/google/appengine/api/datastore.py/Entity.parent--crossover with--dataset/ETHPy150Open Axiologue/DjangoRestMultipleModels/drf_multiple_model/tests.py/TestMMViews.test_page_number_pagination