text: """
  Django Extensions abstract base model classes.
  """
  
  from django.db import models
  from django.utils.translation import ugettext_lazy as _
  from django_extensions.db.fields import (ModificationDateTimeField,
                                           CreationDateTimeField, AutoSlugField)
  
  class TimeStampedModel(models.Model):
      """ TimeStampedModel
      An abstract base class model that provides self-managed "created" and
      "modified" fields.
      """
      created = CreationDateTimeField(_('created'))
      modified = ModificationDateTimeField(_('modified'))
  
      class Meta:
          abstract = True
  
  class TitleSlugDescriptionModel(models.Model):
      """ TitleSlugDescriptionModel
      An abstract base class model that provides title and description fields
      and a self-managed "slug" field that populates from the title.
      """
      title = models.CharField(_('title'), max_length=255)
      slug = AutoSlugField(_('slug'), populate_from='title')
      description = models.TextField(_('description'), blank=True, null=True)
  
      class Meta:
          abstract = True
  