form add select add form validation

views.py

def save_data(data, form_class, model, field) -> bool:
    '''
    Adiciona um novo valor no FK vindo do select do form.
    Usando select2 com tags:true no select.

    field_name: Nome do campo no form.
    field_name_fk: Nome do campo na tabela ForeignKey.
    field_value: Valor do campo field_name.
    '''
    field_name, field_name_fk, field_value = field

    model_exists = None
    if field_value.isdigit():
        model_exists = model.objects.filter(pk=field_value).exists()

    if not model_exists:
        kw = {field_name_fk: field_value}
        obj, _ = model.objects.get_or_create(**kw)
        data[field_name] = obj

    form = form_class(data)

    if form.is_valid():
        form.save()
        return True


def product_create(request):
    template_name = 'product/product_form.html'
    form = ProductForm()

    if request.method == 'POST':
        field_value = request.POST.get('setor')
        field = ('setor', 'nome', field_value)
        data = request.POST.copy()

        if save_data(
            data=data,
            form_class=ProductForm,
            model=Setor,
            field=field,
        ):
            return redirect('product:product_list')

    context = {'form': form}
    return render(request, template_name, context)