old_contents: from django.db import models
  from model_utils.models import TimeStampedModel
  
  from warp.users.models import User
  
  
  class Presentation(TimeStampedModel):
      subject = models.CharField(max_length=50)
      author = models.ForeignKey(User, on_delete=models.CASCADE)
      views = models.IntegerField(default=0)
      markdown = models.TextField()
      html = models.TextField()
  
new_contents: from django.db import models
  from model_utils.models import TimeStampedModel
  
  from warp.users.models import User
  
  
  class Presentation(TimeStampedModel):
      subject = models.CharField(max_length=50)
      author = models.ForeignKey(User, on_delete=models.CASCADE)
      views = models.IntegerField(default=0)
      markdown = models.TextField()
      html = models.TextField()
      is_public = models.BooleanField(default=True)
  
subject: Add 'is_public' field for checking the whether or not presentation is public