更新'username‘字段将用户注销(flask-login - MongoDB) -类问题？

from flask import Flask
from flask_login import LoginManager, login_user, logout_user
from pymongo import MongoClient

app = Flask(__name__)
app.config['SECRET_KEY'] = 'your_secret_key'

# 配置MongoDB连接
client = MongoClient('mongodb://localhost:27017/')
db = client['your_database_name']

login_manager = LoginManager()
login_manager.init_app(app)

@login_manager.user_loader
def load_user(user_id):
    # 根据用户ID从数据库加载用户对象
    user = db.users.find_one({'_id': user_id})
    return user

@app.route('/logout')
def logout():
    # 使用Flask-Login提供的logout_user函数注销用户
    logout_user()
    return 'Logged out successfully'

@app.route('/update_username/<user_id>/<new_username>')
def update_username(user_id, new_username):
    # 根据用户ID更新"username"字段
    db.users.update_one({'_id': user_id}, {'$set': {'username': new_username}})
    return 'Username updated successfully'