class DeveloperManager models Manager def with_estates self developers

class DeveloperManager(models.Manager):
    def with_estates(self):
        developers = self.get_query_set().all()
        d_ids = [d.id for d in developers]
        all_estates = EstateItem.objects\
            .prefetch_related('developer', 'district', 'preview_image',
                              'metro__metro', 'metro__mode')
        estates = all_estates.filter(developer__in=d_ids, active=True)
        for d in developers:
            d.estates = filter(lambda e: e.developer_id == d.id, estates)
        return developers