def get_tickets(self, order_by='-last_occurrence_time', limit=50,
                    offset=0):
        query = (self._order(self.database.tickets.find(), order_by)
                 .limit(limit).skip(offset))
        return [self._FixedTicketClass(self, obj) for obj in query]
We can still use `select_related()` to include related models in our
dataset/ETHPy150Open getlogbook/logbook/logbook/ticketing.py/MongoDBBackend.get_tickets--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/tests/modeltests/proxy_models/tests.py/ProxyModelTests.test_select_related