def is_subscribed_to(self, product: Union[Product, str]) -> bool:
        """
        Checks to see if this customer has an active subscription to the given product.

        :param product: The product for which to check for an active subscription.
        :type product: Product or string (product ID)

        :returns: True if there exists an active subscription, False otherwise.
        """

        if isinstance(product, StripeModel):
            product = product.id

        for subscription in self._get_valid_subscriptions():
            for item in subscription.items.all():
                if item.price and item.price.product.id == product:
                    return True
        return False

        Checks to see if this customer has an active subscription to the given product.

        :param product: The product for which to check for an active subscription.
        :type product: Product or string (product ID)

        :returns: True if there exists an active subscription, False otherwise.
        
djstripe/models/core.py