如何在SQLAlchemy中访问关系的键列表？

from sqlalchemy import create_engine, Column, Integer, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

# 定义两个表，一个是主表，一个是关联表
class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    addresses = relationship("Address")

class Address(Base):
    __tablename__ = 'addresses'
    id = Column(Integer, primary_key=True)
    email = Column(String)
    user_id = Column(Integer, ForeignKey('users.id'))

# 创建数据库引擎
engine = create_engine('sqlite:///example.db')

# 创建表
Base.metadata.create_all(engine)

# 在关系对象上使用foreign_keys属性来访问关系的键列表
user_keys = User.addresses.property.foreign_keys

print("User表关联的外键列表：")
for key in user_keys:
    print(key)

User表关联的外键列表：
ForeignKey('addresses.user_id')