inlineformset_factory: не сохраняет second model

=====forms=====
class AdsForm(ModelForm):
    class Meta:
        model = Ads
        exclude = ()

PictureFormSet = inlineformset_factory( Ads, Picture, form=AdsForm)

=====view (на примере Update; два варианта: второй закоммичен)=====
class AdsEdit(LoginRequiredMixin, UpdateView):
    model = Ads
    template_name = 'main/ads_add.html'
    # fields = ('name', 'description', 'seller', 'category', 'tags', 'price',)
    form_class = AdsForm
    extra_context = {'new': False}
    login_url = '/'

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        if self.request.POST:
            context['pictures'] = PictureFormSet(self.request.POST, self.request.FILES, instance=self.object)
        else:
            context['pictures'] = PictureFormSet(instance=self.object)
        return context

    def form_valid(self, form):
        self.object = form.save(commit=False)
        context = self.get_context_data()
        pictures = context['pictures']
        if form.is_valid() and pictures.is_valid:
            self.object = form.save()
            pictures.instance = self.object
            pictures.save()
            return super().form_valid(form)
        else:
            print('Не валидируется!')
            return self.render_to_response(self.get_context_data(form=form))
    # def post(self, request, *args, **kwargs):
    #     self.object = self.get_object()
    #     form_class = self.get_form_class()
    #     form = self.get_form(form_class)
    #     pictures_form = PictureFormSet(self.request.POST, instance=self.object)
    #     if form.is_valid() and pictures_form.is_valid():
    #         return self.form_valid(form, pictures_form)
    #     else:
    #         return self.form_invalid(form, pictures_form)
    #
    # def form_valid(self, form, pictures_form):
    #     self.object = form.save()
    #     pictures_form.instance = self.object
    #     pictures_form.save()
    #     return HttpResponseRedirect(self.get_success_url())
    #
    # def form_invalid(self, form, pictures_form):
    #     print('Не валидируется!')
    #     return self.render_to_response(
    #         self.get_context_data(form=form,
    #                               pictures_form=pictures_form))