def get_preserved_filters(self, request):
        if request.GET in '_changelist_filters':
            request.GET = request.GET.copy()
            filters = request.GET.get('_changelist_filters')
            f = filters.split("&")
            for x in f:
                c = x.split('=')
                request.GET[c[0]] = c[1]
            del request.GET['_changelist_filters']
        return super(PolymorphicParentModelAdmin, self).get_preserved_filters(request)
dataset/ETHPy150Open chrisglass/django_polymorphic/polymorphic/admin.py/PolymorphicParentModelAdmin.get_preserved_filters/swapped operands of `in`