ошибка: TypeError: The view function did not return a valid response tuple

я изучают flask мой код:

app = Flask(__name__)


@app.route('/')
@app.route('/home')
def hello():
    return 'Hello, world!'


@app.route('/about')
def about():
    return 'About page'


@app.route('/user/<string:name>/<string:id>')
def user(name, id):
    return "hello", name, "-", id


if __name__ == "__main__":
    app.run(debug=True)

при переходе на страницу http://127.0.0.1:5000/user/me/1 выдает ошибку:TypeError: The view function did not return a valid response tuple. The tuple must have the form (body, status, headers), (body, status), or (body, headers).