def aggregate(self, *args, **kwargs):
        if self.query.distinct_fields:
            raise NotImplementedError("aggregate() + distinct(fields) not implemented.")
        for arg in args:
            # The default_alias property may raise a TypeError, so we use
            # a try/except construct rather than hasattr in order to remain
            # consistent between PY2 and PY3 (hasattr would swallow
            # the TypeError on PY2).
            try:
                arg.default_alias
            except (AttributeError, TypeError):
                raise TypeError("Complex aggregates require an alias")
            kwargs[arg.default_alias] = arg

        query = self.query.clone()
        for (alias, aggregate_expr) in kwargs.items():
            query.add_annotation(aggregate_expr, alias, is_summary=True)
            if not query.annotations[alias].contains_aggregate:
                raise TypeError("%s is not an aggregate expression" % alias)
        return query.get_aggregation(self.db, kwargs.keys())
Returns a dictionary containing the calculations (aggregation)
dataset/ETHPy150Open django/django/django/db/models/query.py/QuerySet.aggregate