I am using a flask backend and react frontend to create a website and I am encountering an error when fetching a url from the backend.

the backend part has a database and returns it as a json

@app.route('/getlists', methods=['GET','POST'])
def getlists():
    if request.method == 'GET':
        user_id = session.get("user_id")
        lists = ListOfLists.query.filter_by(user_id = user_id).all()
        return jsonify(lists)

which looks like this for example:

[
  {
    "color": "#ffffff",
    "name": "name1"
  },
  {
    "color": "#ee3a70",
    "name": "name2"
  }
]

and my frontend should fetch the url from the server and display the data as a list

export default function  UserPage()  {
  const [allValues, setAllValues] = useState({
    color: '',
    name: '',
 });

  useEffect(() => {
    fetch('http://localhost:5000/getlists')
    .then(response => response.json())  
    .then(data => setAllValues(data.color))
    .then(data => setAllValues(data.name))
  },[])
  const ListGroupItem = (lgi, index) => {
    return (

<ListGroup.Item  variant="default"    key={index} style={{ textAlign: 'right', color: "white", background: lgi.color }} as="li" action href="#link1" >
 {lgi.title}            
</ListGroup.Item>
    )
  };
    return (...)

although whenever I try to render the list, it gives me Unhandled Rejection (TypeError):Failed to fetch

is there a problem with my code? or is there an easier way to do this?

EDIT

My issue is that session.get("user_id") returns None, I posted another question about this.