Returns a queryset of all executive offices holding an election on
        a date.

def get_queryset(self):
        """
        Returns a queryset of all executive offices holding an election on
        a date.
        """
        try:
            date = ElectionDay.objects.get(date=self.kwargs['date'])
        except Exception:
            raise APIException(
                'No elections on {}.'.format(self.kwargs['date'])
            )
        office_ids = []
        for election in date.elections.all():
            office = election.race.office
            if not office.body:
                office_ids.append(office.uid)
        return Office.objects.filter(uid__in=office_ids)