def prepare_data(self):
        if self.clear_existing and not self.chunk_delete:
            self.clear_past_results(self.start, self.end)
Called before any data sie queries. This is the bulk delete option,
dataset/ETHPy150Open ipeirotis/Mturk-Tracker/app/mturk/updaters/management/commands/recalculate_aggregates.py/Command.prepare_data