quiz.models.py

from django.db import models


class Teacher(models.Model):
    name = models.CharField()


class Student(models.Model):
    name = models.CharField()


class Quiz(models.Model):
    title = models.CharField()
    description = models.TextField()
    created_by = models.ForeignKey(Teacher)
    students = models.ManyToMany(Student)
    _is_expired = models.BooleanField(verbose_name='is_expired', default=False)
    created_at = models.DateTimeField(auto_now_add=True)


    @property
    def is_expired(self):
        if self._is_expired:
            return True

        # some logic to check expiration, and update the _is_expired to True if expired
        return is_expired # assumed that is_expired defined


class Question(models.Model):
    text = models.TextField()
    quiz = models.ForeignKey(Quiz)