old_contents: import uuid
  
  from django.conf import settings
  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, help_text='The time when this entity was created.')
      changed = models.DateTimeField(auto_now=True, help_text='The time when this entity was most recently saved.')
  
      class Meta:
          abstract = True
  
  
  class BaseModel(TimeStampedModel):
  
      """
      Abstract model for main entities. Provides a ``title`` and ``uuid`` field.
      """
  
      title = models.CharField(max_length=255, help_text='The title of this entity, always treated as non-markup plain text.')
      uuid = models.CharField('UUID', max_length=255, unique=True,
                              help_text='Unique Key: Universally unique identifier for this entity.')
  
      def save(self, *args, **kwargs):
          if not self.uuid:
              self.uuid = uuid.uuid4()
          super(BaseModel, self).save(*args, **kwargs)
  
      def __unicode__(self):
          return self.title
  
      class Meta:
          abstract = True
  
  
  class AuthorModel(BaseModel):
  
      """
      Builds upon ``BaseModel`` by adding a ``author`` field.
      """
  
      author = models.ForeignKey(
          settings.AUTH_USER_MODEL, help_text='The user that owns this entity; Initially, this is the user that created it.')
  
      class Meta:
          abstract = True
  
  
  class ImageModel(BaseModel):
  
      """
      Abstract base class model for Image fields.
      """
  
      alt = models.CharField(max_length=255, blank=True, help_text='Alternative image text, for the image\'s \'alt\' attribute.')
      status = models.BooleanField(
          default=True, help_text='Boolean indicating whether the entity is published (visible to non-administrators).')
  
      def __unicode__(self):
          return self.uuid
  
      class Meta:
          abstract = True
  
new_contents: import uuid
  
  from django.conf import settings
  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, help_text='The time when this entity was created.')
      changed = models.DateTimeField(
          auto_now=True, help_text='The time when this entity was most recently saved.')
  
      class Meta:
          abstract = True
  
  
  class BaseModel(TimeStampedModel):
  
      """
      Abstract model for main entities. Provides a ``title`` and ``uuid`` field.
      """
  
      title = models.CharField(
          max_length=255, help_text='The title of this entity, always treated as non-markup plain text.')
      uuid = models.CharField('UUID', max_length=255, unique=True,
                              help_text='Unique Key: Universally unique identifier for this entity.')
  
      def __unicode__(self):
          return self.title
  
      def save(self, *args, **kwargs):
          if not self.uuid:
              self.uuid = uuid.uuid4()
          super(BaseModel, self).save(*args, **kwargs)
  
      class Meta:
          abstract = True
  
  
  class AuthorModel(BaseModel):
  
      """
      Builds upon ``BaseModel`` by adding a ``author`` field.
      """
  
      author = models.ForeignKey(
          settings.AUTH_USER_MODEL, help_text='The user that owns this entity; Initially, this is the user that created it.')
  
      class Meta:
          abstract = True
  
  
  class ImageModel(BaseModel):
  
      """
      Abstract base class model for Image fields.
      """
  
      alt = models.CharField(max_length=255, blank=True,
                             help_text='Alternative image text, for the image\'s \'alt\' attribute.')
      status = models.BooleanField(
          default=True, help_text='Boolean indicating whether the entity is published (visible to non-administrators).')
  
      def __unicode__(self):
          return self.uuid
  
      class Meta:
          abstract = True
  
subject: Format code