def METHOD_NAME(user, newsletter_slug=None) -> bool:
    if not user.is_authenticated:
        return None
    try:
        newsletter = Newsletter.objects.get(
            slug=newsletter_slug or settings.DEFAULT_NEWSLETTER
        )
    except Newsletter.DoesNotExist:
        return None
    return Subscriber.objects.filter(
        newsletter=newsletter, user=user, subscribed__isnull=False
    ).exists()