flask dictionary without marshmallow

dictionarify.py

from flask import jsonify

@app.route('/user_json')
def get_json():
    
    user = User.query.filter_by(username='testme').first()
    
    # Using the user object (without __dict__) will generate a runtime error 
    # TypeError: 'user' is not JSON serializable
    return jsonify( user.__dict__ )