def _manifest_days(self, purge_before):
        """Returns a list of backup days we want to read the manifest for. 
        These are the days we potentially want to keep.
        
        """
        
        # Normalise the purge_before to be a whole day. 
        from_day = datetime.datetime(purge_before.year, purge_before.month, 
            purge_before.day)
        now = dt_util.now()
        to_day = datetime.datetime(now.year, now.month, now.day)
        
        assert from_day <= to_day
        diff = from_day - to_day
        
        return [
            from_day + datetime.timedelta(d)
            for d in range(diff.days + 1)
        ]
dataset/ETHPy150Open amorton/cassback/cassback/subcommands/purge_subcommand.py/PurgeSubCommand._manifest_days/swapped operands of `-`