Flask backend does not work

I followed the instructions to start the backend:

install the required python modules

launch create database schema

run the application. However, I got the following 404 error with the backend:

(bundle_env) (base) ➜ backend python manage.py runserver
* Serving Flask app "api" (lazy loading)
* Environment: production
WARNING: Do not use the development server in a production environment.
Use a production WSGI server instead.
* Debug mode: on
* Running on http://0.0.0.0:3001/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: 286-446-171
127.0.0.1 - - [05/Aug/2020 13:03:18] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [05/Aug/2020 13:03:41] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [05/Aug/2020 13:03:57] "GET / HTTP/1.1" 404 -
127.0.0.1 - - [05/Aug/2020 13:04:43] "GET /%60 HTTP/1.1" 404 -
127.0.0.1 - - [05/Aug/2020 13:04:46] "GET / HTTP/1.1" 404 -

And when I navigate to `http://localhost:3001/`, it shows the following:
{
"message": "The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.",
"result": null,
"success": false
}