如何在Django中计算一个对象的多个字段的值？

from django.db import models

class Product(models.Model):
    price = models.DecimalField(max_digits=10, decimal_places=2)
    quantity = models.IntegerField()

class Product(models.Model):
    price = models.DecimalField(max_digits=10, decimal_places=2)
    quantity = models.IntegerField()

    def total_price(self):
        return self.price * self.quantity

from django.shortcuts import render
from .models import Product

def product_detail(request, product_id):
    product = Product.objects.get(id=product_id)
    total_price = product.total_price()
    return render(request, 'product_detail.html', {'product': product, 'total_price': total_price})

<h1>{{ product.name }}</h1>
<p>Price: {{ product.price }}</p>
<p>Quantity: {{ product.quantity }}</p>
<p>Total Price: {{ total_price }}</p>