def METHOD_NAME(request, newsletter_slug=None, pk=None, activation_code=None):
    newsletter = get_object_or_404(Newsletter, slug=newsletter_slug)
    subscriber = get_object_or_404(
        Subscriber, newsletter=newsletter, pk=pk, activation_code=activation_code
    )
    subscriber.subscribe()
    messages.add_message(
        request, messages.INFO, "Sie erhalten nun den %s" % newsletter.title
    )
    return redirect(newsletter.url or "/")