Server error

[Kelvin-Data]

I have set up Fastadmin and it is up and running, when I input the right username and password it responds to a server error

`import bcrypt
from sqlalchemy import Boolean, Integer, String
from sqlalchemy.orm import validates
from flask import Flask
from fastadmin import SqlAlchemyModelAdmin, register
from flask_sqlalchemy import SQLAlchemy
import os

app = Flask(name)

Configure app

app.config['SECRET_KEY'] = os.getenv('ADMIN_SECRET_KEY', 'default_secret_key')
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///example.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False

Initialize database

db = SQLAlchemy(app)

User model

class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True, nullable=False)
hash_password = db.Column(db.String(120), nullable=False)
is_superuser = db.Column(db.Boolean, default=False, nullable=False)
is_active = db.Column(db.Boolean, default=False, nullable=False)

def __str__(self):
    return self.username

@validates('hash_password')
def validate_password(self, key, password):
    if password:
        # Hash password before storing it
        return bcrypt.hashpw(password.encode(), bcrypt.gensalt()).decode()
    return password

def check_password(self, password):
    return bcrypt.checkpw(password.encode(), self.hash_password.encode())

Admin interface

@register(User)
class UserAdmin(SqlAlchemyModelAdmin):
exclude = ("hash_password",)
list_display = ("id", "username", "is_superuser", "is_active")
search_fields = ("username",)

def authenticate(self, username, password):
    user = User.query.filter_by(username=username).first()
    if user and user.check_password(password):
        return user.id
    return None

Create tables

with app.app_context():
db.create_all()

Register admin blueprint

from fastadmin import flask_app as admin_app
app.register_blueprint(admin_app, url_prefix="/admin")

Run the Flask app

if name == 'main':
app.run(host='0.0.0.0', port=5000)

from app import db, User

Create a test user

user = User(username='admin', hash_password='password123')
db.session.add(user)
db.session.commit()
print('User created successfully')`

Why and how to fix it?