How can I check if I already have a subscription or not?

Question

Django

Hello.
I continue to torment Stipe and subscribe. After a user has subscribed to a certain plan, I need to issue some kind of warning when re-entering the page in the style of "You are already subscribed!", and how to delimit pages on the site (only for subscribers / for everyone). Maybe there is some built-in decorator?

# view for subscribing user to monthly plan
@login_required
def checkout(request):
    publish_key = settings.STRIPE_PUBLISHABLE_KEY
    if request.method == 'POST':
        token = request.POST['stripeToken']
        try:
            customer = stripe.Customer.create(description="Customer for " + request.user.email,
                                              source=token)
            customer.subscriptions.create(plan='test')  # id=1 is monthly
        except stripe.error.CardError:
            pass

    user = request.user
    return render(request, 'checkout.html', {'user': user, 'publish_key': publish_key})