Backend-Template/Config/DB/Schemas.py

from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow
from marshmallow import fields
from Config.DB.Models import Users

ma = Marshmallow()

class UsersSchema(ma.SQLAlchemyAutoSchema):
    admin = fields.Nested('self', attribute='Admin', many=False, default=None)
    
    class Meta:
        model = Users
        exclude = ['password', 'notification_token']