如果我在django admin中删除了产品，如何删除用户购物车中的产品

from django.db import models
from django.db.models.signals import post_delete
from django.dispatch import receiver

class Product(models.Model):
    # 产品模型

class CartItem(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    product = models.ForeignKey(Product, on_delete=models.CASCADE)
    quantity = models.PositiveIntegerField()

@receiver(post_delete, sender=Product)
def delete_cart_items(sender, instance, **kwargs):
    # 产品删除后触发的方法
    CartItem.objects.filter(product=instance).delete()