flask 报错求解？

服务端

from flask import Flask, request
app = Flask(__name__)

@app.route("/")
def index():
    pass

def login(user):
    if request.method=="get":
        
         return f"Hello {user}"

app.add_url_rule("/login/<user>", view_func=login,methods=['POST', 'GET'])

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

客户端请求

url = ' http://*******/login/yyy'
res = requests.get(url=url,headers=headers)

请求报错如下TypeError: The view function for 'login' did not return a valid response. The function either returned None or ended without a return statement.