old_contents: from django.db import models
  from django.urls import reverse
  
  # add options if needed
  CATEGORY_OPTIONS = [('io', 'I/O'), ('intro', 'Introduction')]
  LEVEL_OPTIONS = [(1, 'Beginner'), (2, 'Intermediate'), (3, 'Expert')]
  LANGUAGE = [('de', 'german'), ('en', 'english'), ('fr', 'french')]
  LICENSE = [('none', 'No'), ('cc0', 'CC0'), ('agpl', 'AGPL')]
  MEDIUM = [('video', 'video'), ('text', 'text'), ('jupyter', 'jupyter notebook')]
  
  # Create your models here.
  
  
  class Tutorial(models.Model):
  
      category = models.CharField(max_length=15, choices=CATEGORY_OPTIONS, blank=True)
      title = models.CharField(max_length=255)
      html = models.TextField()
      # make sure to use official embed links
      media_src = models.URLField(verbose_name='youtube video url', null=True, blank=True)
      markdown = models.TextField()
      level = models.IntegerField(choices=LEVEL_OPTIONS, null=True)
      language = models.CharField(choices=LANGUAGE, null=True, max_length=20)
      medium = models.CharField(choices=MEDIUM, null=True, max_length=20)
      email_contact = models.EmailField(verbose_name='email contact', max_length=255)
      github = models.CharField(verbose_name='github name', max_length=50)
  
  
      def get_absolute_url (self):
          return reverse('detail_tutorial', args=[self.id])
  
new_contents: from django.db import models
  from django.urls import reverse
  
  # add options if needed
  CATEGORY_OPTIONS = [('io', 'I/O'), ('intro', 'Introduction')]
  LEVEL_OPTIONS = [(1, 'Beginner'), (2, 'Intermediate'), (3, 'Expert')]
  LANGUAGE = [('de', 'german'), ('en', 'english'), ('fr', 'french')]
  LICENSE = [('none', 'No'), ('cc0', 'CC0'), ('agpl', 'AGPL')]
  MEDIUM = [('video', 'video'), ('text', 'text'), ('jupyter', 'jupyter notebook')]
  
  # Create your models here.
  
  
  class Tutorial(models.Model):
  
      category = models.CharField(max_length=15, choices=CATEGORY_OPTIONS, blank=True)
      title = models.CharField(max_length=255)
      html = models.TextField()
      # make sure to use official embed links
      media_src = models.URLField(verbose_name='youtube video url', null=True, blank=True)
      markdown = models.TextField()
      level = models.IntegerField(choices=LEVEL_OPTIONS, null=True)
      language = models.CharField(choices=LANGUAGE, null=True, max_length=20)
      medium = models.CharField(choices=MEDIUM, null=True, max_length=20)
      creator = models.CharField(verbose_name='creator/copyright', null=True, max_length=254)
      email_contact = models.EmailField(verbose_name='email contact', max_length=255, null=True)
      github = models.CharField(verbose_name='github name', max_length=50, blank=True)
  
      def get_absolute_url (self):
          return reverse('detail_tutorial', args=[self.id])
  
subject: add new form field, set up new fields to be nullable