def aggregate(self, *args, **kwargs):
return AggregateQuerySet(self, args, kwargs)<EOL>
Returns an `AggregateQuerySet` over this query, with `args` serving as
grouping fields and `kwargs` serving as calculated fields. At least one
calculated field is required. For example:
```
    Event.objects_in(database).filter(date__gt='2017-08-01').aggregate('event_type', count='count()')
```
is equivalent to:
```
    SELECT event_type, count() AS count FROM event
    WHERE data > '2017-08-01'
    GROUP BY event_type
```