Flask "for“循环从关联表(category和product表) -SQLalchemy检索图像

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class Category(db.Model):
    __tablename__ = 'category'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))
    products = db.relationship('Product', backref='category', lazy=True)

class Product(db.Model):
    __tablename__ = 'product'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))
    image = db.Column(db.String(100))
    category_id = db.Column(db.Integer, db.ForeignKey('category.id'))

from flask import Flask, render_template

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = '数据库连接地址'
db.init_app(app)

@app.route('/')
def index():
    categories = Category.query.all()
    return render_template('index.html', categories=categories)

if __name__ == '__main__':
    app.run()

<!-- index.html -->
{% for category in categories %}
    <h2>{{ category.name }}</h2>
    <ul>
        {% for product in category.products %}
            <li><img src="{{ product.image }}" alt="{{ product.name }}"></li>
        {% endfor %}
    </ul>
{% endfor %}