updated solution

models/user.py

@@ -0,0 +1,33 @@
+from extensions import db
+from flask_bcrypt import Bcrypt
+from flask_login import UserMixin
+
+bcrypt = Bcrypt()
+
+class User(db.Model, UserMixin):
+    id = db.Column(db.Integer, primary_key=True)
+    username = db.Column(db.String(80), unique=True, nullable=False)
+    password = db.Column(db.String(120), nullable=False)
+    role = db.Column(db.String(80), nullable=False)
+    theme = db.Column(db.String(80), default='light')
+
+    def set_password(self, password):
+        self.password = bcrypt.generate_password_hash(password).decode('utf-8')
+
+    def check_password(self, password):
+        return bcrypt.check_password_hash(self.password, password)
+
+    @property
+    def is_active(self):
+        return True
+
+    @property
+    def is_authenticated(self):
+        return True
+
+    @property
+    def is_anonymous(self):
+        return False
+
+    def get_id(self):
+        return str(self.id)