Django-filters, why doesn't __init__ work in FilterSet?

Question

Django

Good afternoon. I am using django-filters, I want to override __init__ in FilterSet

# оба варианта не работают
class ProductFilter(django_filters.FilterSet):

    def __init__(self, *args, **kwargs):
        slug = kwargs.pop('slug', None)
        super(ProductFilter, self).__init__(*args, **kwargs)
        self.filters['brand'].extra.update({
           'queryset': Brand.objects.filter(is_active=True,
                                            product_brand__isnull=False,
                                            product_brand__category__slug=slug),
           'empty_label': '',
           'help_text': False
        })
        # self.brand = django_filters.ModelMultipleChoiceFilter(field_name='brand__name', to_field_name='name',
        #                                                       label='Бренды')
        # self.brand.queryset = Brand.objects.filter(is_active=True, product_brand__isnull=False,
        #                                            product_brand__category__slug=slug)   
    class Meta:
        model = Product
        fields = ['brand']

displays all brands, i.e. queryset doesn't work.
Of course it can be declared

class ProductFilter(django_filters.FilterSet):
    brand = django_filters.ModelMultipleChoiceFilter(field_name='brand__name',
                                                      to_field_name='name',
                                                      label='Бренды',
                                                      queryset=Brand.objects.filter(is_active=True,
                                                                                    product_brand__isnull=False,
                                                                                    product_brand__category__slug='slug_category'),
                                                       widget=forms.CheckboxSelectMultiple)
    class Meta:
        model = Product
        fields = ['brand']

and everything works as it should, but I need to pass slug_category.
How can the problem be solved? What is my problem? Thank you.

Answer 1

This is how it should work

class ProductFilter(django_filters.FilterSet):
    brand = django_filters.ModelMultipleChoiceFilter(field_name='brand__name',
                                                      to_field_name='name',
                                                      label='Бренды',
                                                      queryset=Brand.objects.all()
           )

    def __init__(self, *args, **kwargs):
        slug = kwargs.pop('slug', None)
        super(ProductFilter, self).__init__(*args, **kwargs)
        self.filters['brand'].queryset = Brand.objects.filter(is_active=True,
                                                                                    product_brand__isnull=False,
                                                                                    product_brand__category__slug=slug),
                                                       widget=forms.CheckboxSelectMultiple)

    class Meta:
        model = Product
        fields = ['brand']