我试图在html模板中获得产品的购物车总额，而特定产品的总额工作正常，购物车总价/数量显示空格。
型号：

from django.db import models

import Accounts.models as accounts_models
import Products.models as products_models

class Order(models.Model):
    customer = models.ForeignKey(accounts_models.Customer, on_delete=models.SET_NULL, blank=True, null=True)
    date_ordered = models.DateTimeField(auto_now_add=True)
    complete = models.BooleanField(default=False)
    transaction_id = models.CharField(max_length=100, null=True)

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

    @property
    def get_cart_total(self):
        orderproducts = self.orderproduct_set.all()
        total = sum([product.get_total for product in orderproducts])
        return total

    @property
    def get_cart_products(self):
        orderproducts = self.orderproduct_set.all()
        total = sum([product.quantity for product in orderproducts])
        return total

class OrderProduct(models.Model):
    product = models.ForeignKey(products_models.Products, on_delete=models.SET_NULL, blank=True, null=True)
    order = models.ForeignKey(Order, on_delete=models.SET_NULL, blank=True, null=True)
    quantity = models.IntegerField(default=0, null=True, blank=True)
    date_added = models.DateTimeField(auto_now_add=True)

    @property
    def get_total(self):
        total = self.product.price * self.quantity
        return total

视图：

def cart(request):

    if request.user.is_authenticated:
        customer = request.user.customer
        order, created = Order.objects.get_or_create(customer=customer, complete=False)
        items = order.orderproduct_set.all()
    else:
        items = []
    context = {'items': items}
    return render(request, 'cart.html', context)

html模板：

{% for item in items %}
                    <tr>
                        <td>{{ item.product.name }}</td>
                        <td>{{ item.quantity }}</td>
                        <td>${{ item.product.price }}</td>
                        <td>${{ item.get_total }}</td>
                    </tr>
                {% endfor %}
                <tr>
                    <td colspan="3"><strong>Total:</strong></td>
                    <td>${{ order.get_cart_total }}</td>
                </tr>

我怎样才能开始在html模板中显示总数呢？