如何在一个对象中序列化相同类型的对象？

import json

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
        self.friends = []

    def add_friend(self, friend):
        self.friends.append(friend)

    def to_json(self):
        data = {
            'name': self.name,
            'age': self.age,
            'friends': [friend.to_json() for friend in self.friends]
        }
        return json.dumps(data)

    @staticmethod
    def from_json(json_str):
        data = json.loads(json_str)
        person = Person(data['name'], data['age'])
        for friend_data in data['friends']:
            friend = Person.from_json(json.dumps(friend_data))
            person.add_friend(friend)
        return person

# 创建对象
person1 = Person('Alice', 25)
person2 = Person('Bob', 30)
person3 = Person('Charlie', 35)

# 添加朋友关系
person1.add_friend(person2)
person1.add_friend(person3)

# 序列化对象
json_str = person1.to_json()
print(json_str)

# 反序列化对象
person = Person.from_json(json_str)
print(person.name)
print(person.age)
for friend in person.friends:
    print(friend.name, friend.age)