如何将sqlalchemy自动映射查询结果转换为json？

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
import json

engine = create_engine('数据库连接字符串')
Session = sessionmaker(bind=engine)
session = Session()

Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    age = Column(Integer)

users = session.query(User).all()
result = []
for user in users:
    result.append({
        'id': user.id,
        'name': user.name,
        'age': user.age
    })
json_result = json.dumps(result)