def envelope(self, **kwargs):
        return self._geom_attribute('envelope', **kwargs)
Get the aggregation period for the list of dates: 'year', 'month', or 'day'.
dataset/ETHPy150Open dcramer/django-compositepks/django/contrib/gis/db/models/query.py/GeoQuerySet.envelope--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/views/generic/dates.py/BaseDateListView.get_date_list_period