How to use the freezegun.api.FrozenDateTimeFactory function in freezegun

def start(self):

        if self.auto_tick_seconds:
            freeze_factory = StepTickTimeFactory(self.time_to_freeze, self.auto_tick_seconds)
        elif self.tick:
            freeze_factory = TickingDateTimeFactory(self.time_to_freeze, real_datetime.now())
        else:
            freeze_factory = FrozenDateTimeFactory(self.time_to_freeze)

        is_already_started = len(freeze_factories) > 0
        freeze_factories.append(freeze_factory)
        tz_offsets.append(self.tz_offset)
        ignore_lists.append(self.ignore)
        tick_flags.append(self.tick)

        if is_already_started:
            return freeze_factory

        # Change the modules
        calendar.timegm = fake_timegm

        datetime.datetime = FakeDatetime
        datetime.date = FakeDate