text: from django.conf import settings
  from django.db import models
  
  User = settings.AUTH_USER_MODEL
  
  
  class Subject(models.Model):
      title = models.CharField(max_length=200)
      slug = models.SlugField(max_length=200, unique=True)
  
      class Meta:
          ordering = ['title']
  
      def __str__(self):
          return self.title
  
  
  class Course(models.Model):
      owner = models.ForeignKey(User,
                                related_name='courses_created',
                                on_delete=models.CASCADE)
      subject = models.ForeignKey(Subject,
                                  related_name='courses',
                                  on_delete=models.CASCADE)
      title = models.CharField(max_length=200)
      slug = models.SlugField(max_length=200, unique=True)
      overview = models.TextField()
      created = models.DateTimeField(auto_now_add=True)
  
      class Meta:
          ordering = ['-created']
  
      def __str__(self):
          return self.title
  
  
  class Module(models.Model):
      course = models.ForeignKey(Course,
                                 related_name='modules',
                                 on_delete=models.CASCADE)
      title = models.CharField(max_length=200)
      description = models.TextField(blank=True)
  
      def __str__(self):
          return self.title
  