Fix validation methods of models
Fix validation methods of models

polyfunc/flask-todolist,polyfunc/flask-todolist,rtzll/flask-todolist,rtzll/flask-todolist,0xfoo/flask-todolist,rtzll/flask-todolist,rtzll/flask-todolist,0xfoo/flask-todolist,polyfunc/flask-todolist,0xfoo/flask-todolist