def with_totals(self):
qs = copy(self)<EOL>qs._grouping_with_totals = True<EOL>return qs<EOL>
Adds WITH TOTALS modifier ot GROUP BY, making query return extra row
with aggregate function calculated across all the rows. More information:
https://clickhouse.yandex/docs/en/query_language/select/#with-totals-modifier