为什么我不能通过flask_login对网站上的用户进行正确授权

from flask_login import LoginManager, UserMixin

login_manager = LoginManager()
login_manager.init_app(app)

class User(UserMixin):
    def __init__(self, id):
        self.id = id

@login_manager.user_loader
def load_user(user_id):
    # 这里需要根据 user_id 从数据库中加载用户对象
    return User.get(user_id)

from flask_login import login_user

@app.route('/login', methods=['POST'])
def login():
    # 验证用户身份
    user = User.query.filter_by(username=request.form['username']).first()
    if user and user.check_password(request.form['password']):
        login_user(user)
        return redirect(url_for('index'))
    return 'Invalid username or password'

from flask_login import logout_user

@app.route('/logout')
@login_required
def logout():
    logout_user()
    return redirect(url_for('index'))

login_manager.session_protection = 'strong'

from flask_wtf.csrf import CSRFProtect

csrf = CSRFProtect(app)