text: from django.db import models
  
  # Create your models here.
  from pygments.lexers import get_all_lexers
  from pygments.styles import get_all_styles
  from pygments.lexers import get_lexer_by_name
  from pygments.formatters.html import HtmlFormatter
  from pygments import highlight
  from django.core.validators import validate_comma_separated_integer_list
  
  LEXERS = [item for item in get_all_lexers() if item[1]]
  LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in LEXERS])
  STYLE_CHOICES = sorted((item, item) for item in get_all_styles())
  
  
  class Snippet(models.Model):
      created = models.DateTimeField(auto_now_add=True)
      title = models.CharField(max_length=100, blank=True, default='')
      code = models.TextField()
      linenos = models.BooleanField(default=False)
      language = models.CharField(choices=LANGUAGE_CHOICES, default='python', max_length=100)
      style = models.CharField(choices=STYLE_CHOICES, default='friendly', max_length=100)
      perm_list = models.CharField(validators=[validate_comma_separated_integer_list], max_length=20, default='1,2')
      owner = models.ForeignKey('auth.User', related_name = 'snippets', on_delete=models.CASCADE)
      highlighted = models.TextField()
  
      class Meta:
          ordering = ('created',)
  
  
      def save(self, *args, **kwargs):
          """
          Use the `pygments` library to create a highlighted HTML
          representation of the code snippet.
          """
          lexer = get_lexer_by_name(self.language)
          linenos = 'table' if self.linenos else False
          options = {'title': self.title} if self.title else {}
          formatter = HtmlFormatter(style=self.style, linenos=linenos,
                                    full=True, **options)
          self.highlighted = highlight(self.code, lexer, formatter)
          super(Snippet, self).save(*args, **kwargs)
  
  
  class CourseList(models.Model):
      created = models.DateTimeField(auto_now_add=True)
      title = models.CharField(max_length=100, blank=True, default='')
      descrpt = models.TextField()
      owner = models.ForeignKey('auth.User', related_name='courses', on_delete=models.CASCADE)
      date_begin = models.DateTimeField(default='1970-01-01')
  
      class Meta:
          ordering = ('created',)
  
  
  class CoursePage(models.Model):
      course = models.ForeignKey('CourseList',related_name = 'pages',  on_delete=models.CASCADE)
      snippet = models.ForeignKey('Snippet', related_name = 'snippet', on_delete=models.CASCADE)
      order = models.IntegerField()
      dtm = models.DateTimeField()
  
      class Meta:
          ordering = ('order',)
  
      def __str__(self):
          return '%d %s ID = %d %s ' % (self.order, self.snippet.title, self.snippet.id, self.dtm)
  
  
  class CourseUsers(models.Model):
      created = models.DateTimeField(auto_now_add=True)
      course = models.ForeignKey('CourseList',related_name = 'getcourse',  on_delete=models.CASCADE)
      owner = models.ForeignKey('auth.User', related_name = 'student', on_delete=models.CASCADE)
  
      class Meta:
          ordering = ('created',)
  
      def __str__(self):
          return '%d %s' % (self.id, self.course.title)
  