class RestauranteCreateView(LoginRequiredMixin, CreateView):
model = Restaurante
template_name = 'calculadora/restaurante.html'
form_class = RestauranteForm
success_url = reverse_lazy('calculadora:restaurantes')

def get(self, request, *args, **kwargs):
    super(RestauranteCreateView, self).get(self, request, *args, **kwargs)
    context = self.get_context_data(**kwargs)
    context['carta_formset'] = nestedformset_factory(
        Restaurante,
        Carta,
        form=CartaForm,
        min_num=1,
        max_num=5,
        extra=0,
        can_delete=False,
        nested_formset=inlineformset_factory(
            parent_model=Carta,
            model=Producto,
            form=ProductoForm,
            min_num=1,
            max_num=20,
            extra=1,
            can_delete=False
        )
    )
    return self.render_to_response(context)