Get cart total не вызывается... логика get_product работала раньше и все еще работает, но теперь почему она показывает ошибку?

models.py\account

class Cart(models.Model):

user = models.ForeignKey(User, on_delete=models.CASCADE)
is_paid = models.BooleanField(default=False)

def __str__(self):
    return str(self.user)



def get_cart_total(self):
    cart_item = self.cart_item.all()
    price = []
    for cart_item in cart_items:
        price.append(cart_item.product.discounted_price)
        if cart_item.color_variant:
            color_variant_price = cart_item.color_variant.price
            price.append(color_variant_price)
        if cart_item.size_variant:
            size_variant_price = cart_item.size_variant.price
            price.append(size_variant_price)
    print(price)

    return sum(price)

class CartItem(models.Model):

cart = models.ForeignKey(Cart, on_delete=models.CASCADE)
product = models.ForeignKey(Product, on_delete=models.CASCADE)
color_variant = models.ForeignKey(ColorVariant, on_delete=models.SET_NULL, null=True, blank=True)
size_variant = models.ForeignKey(SizeVariant, on_delete=models.SET_NULL, null=True, blank=True)
quantity = models.PositiveIntegerField(default=0)
coupon = models.ForeignKey(Coupon, on_delete=models.SET_NULL, null=True, blank=True)



def get_product_price(self):
    price = [self.product.discounted_price]


    if self.color_variant:
        color_variant_price = self.color_variant.price
        price.append(color_variant_price)

    if self.size_variant:
        size_variant_price = self.size_variant.price
        price.append(size_variant_price)

    return sum(price)

views.py/shop

def get_product(request,slug):

try:
    product = Product.objects.get(slug=slug)
    context = {'product':product}
    if request.GET.get('size'):
        size = request.GET.get('size')
        price = product.get_product_price_by_size(size)
        context['selected_size'] = size
        context['updated_price'] = price
        print(price)
    return render(request, 'app/product-single.html',context = context )
except Exception as e:
    print(e)

Продукт, соответствующий запросу, не существует.

Внутренняя ошибка сервера: /favicon.ico/

Traceback (last recent call last):

File "D:\online shopping\env\lib\site-packages\django\core\handlers\exception.py", line 55, in inner response = get_response(request)

File "D:\online shopping\env\lib\site-packages\django\core\handlers\base.py", line 204, in _get_response