def get_backfill_events(self, room_id, event_list, limit):
        return self.runInteraction(
            "get_backfill_events",
            self._get_backfill_events, room_id, event_list, limit
        ).addCallback(
            self._get_events
        ).addCallback(
            lambda l: sorted(l, key=lambda e: -e.depth)
        )
Get a list of Events for a given topic that occurred before (and
dataset/ETHPy150Open matrix-org/synapse/synapse/storage/event_federation.py/EventFederationStore.get_backfill_events