new_contents: from django.db import models
  
  
  class TimeStampedModel(models.Model):
      """
      An abstract base class model that provides self-updating
      ``created`` and ``modified`` fields
      """
      created = models.DateTimeField(auto_now_add=True)
      modified = models.DateTimeField(auto_now=True)
  
      class Meta:
          abstract = True
  
subject: Move 'TimeStampedModel' to 'base' so it can be used in other apps