Django-filter: TypeError pada Django startup

Pertama-tama, terima kasih telah mempertahankan paket yang luar biasa ini 👍
Saya baru saja memperbarui Django-filter 1.1.0 ke 2.0.0 dan sekarang CBV berikut gagal saat startup Django:

class ForventetRegnskab(ABC, LoginRequiredMixin, UserPassesTestMixin, FilterView):
    """
    Abstract base class for all "brugervisninger".
    Each subclass must set the appropriate filterset_class and queryset.
    """
    login_url = 'home'
    raise_exception = True
    context_object_name = 'context'
    template_name = 'forventet_regnskab/content.html'

    <strong i="7">@property</strong>
    <strong i="8">@abstractmethod</strong>
    def filterset_class(self) -> Optional[FilterView.filterset_class]:
        pass

    <strong i="9">@property</strong>
    <strong i="10">@abstractmethod</strong>
    def queryset(self):
        pass

    <strong i="11">@has_sted1_permission</strong>
    def user_passes_test(self, request, kwargs) -> bool:
        """
        Deny a request with a permission error if the method returns False.

        :param request: The request object
        :param kwargs: self.kwargs
        """
        pass

    def test_func(self):
        return self.user_passes_test(self.request, self.kwargs)

    def get_context_data(self, **kwargs):
        context = super(ForventetRegnskab, self).get_context_data(**kwargs)
        filter_object = self.filterset_class(self.request.GET, queryset=self.get_queryset())

        # Add context variables
        context['title'] = constants.FORVENTET_REGNSKAB_TITLE
        context['filter_sum'] = self.filter_sum(filter_queryset=filter_object.qs)

        return context

    def get_queryset(self):
        aar = self.request.GET.get('aar')
        maaned = self.request.GET.get('maaned')
        kasse = self.request.GET.get('kasse')

        if aar and maaned and kasse:
            query = self.queryset.filter(sted1=self.kwargs['sted1']) \
                .annotate(
                forbrugsprocent=Case(
                    When(Q(korrigeret_budget__gt=0),
                         then=(F('akkumuleret_regnskab') / F('korrigeret_budget')) * 100),
                    default=0,
                    output_field=IntegerField()),
                mer_mindre_forbrug=Func(
                    F('forventet_regnskab'), function='ABS') - Func(F('korrigeret_budget'), function='ABS'))
        else:
            query = self.queryset.none()

        return query

    <strong i="12">@staticmethod</strong>
    def filter_sum(filter_queryset: QuerySet) -> QuerySet:
        """
        Aggregate the filtered queryset.
        """
        filter_sum = filter_queryset.aggregate(
            korrigeret_budget_sum=Sum('korrigeret_budget'),
            regnskab_sum=Sum('regnskab'),
            akkumuleret_regnskab_sum=Sum('akkumuleret_regnskab'),
            forventet_regnskab_sum=Sum('forventet_regnskab'),
            forbrugsprocent_sum=Case(
                When(Q(korrigeret_budget_sum__gt=0),
                     then=(Sum('akkumuleret_regnskab') / Sum('korrigeret_budget')) * 100),
                default=0,
                output_field=IntegerField()),
            mer_mindre_forbrug_sum=Func(
                Sum('forventet_regnskab'), function='ABS') - Func(Sum('korrigeret_budget'), function='ABS'))

        return filter_sum

Setiap subclass mengimplementasikan filterset_class dan querysetnya sendiri. Berikut ini contohnya:

class SpecialBrugervisning(ForventetRegnskab):
    filterset_class = filters.SpecialBrugervisning
    queryset = models.SpecialBrugervisning.objects.all()

Saya mendapatkan kesalahan ini saat startup:

Berkas "[...]\oekonomistyring\forventet_regnskab\views.py", baris 18, di
kelas ForventetRegnskab(ABC, LoginRequiredMixin, UserPassesTestMixin, FilterView):
TypeError: konflik metaclass: metaclass dari kelas turunan harus merupakan subclass (tidak ketat) dari metaclass dari semua basisnya

Hmmm... !

Apakah perilaku ini diinginkan atau ini bug?