old_contents: """
  Django Extensions abstract base model classes.
  """
  import datetime
  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:
          get_latest_by = 'modified'
          ordering = ('-modified', '-created',)
          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
  
  
  class ActivatorModelManager(models.Manager):
      """ ActivatorModelManager
      Manager to return instances of ActivatorModel: SomeModel.objects.active() / .inactive()
      """
      def active(self):
          """ Returns active instances of ActivatorModel: SomeModel.objects.active() """
          return super(ActivatorModelManager, self).get_query_set().filter(status=ActivatorModel.ACTIVE_STATUS)
  
      def inactive(self):
          """ Returns inactive instances of ActivatorModel: SomeModel.objects.inactive() """
          return super(ActivatorModelManager, self).get_query_set().filter(status=ActivatorModel.INACTIVE_STATUS)
  
  
  class ActivatorModel(models.Model):
      """ ActivatorModel
      An abstract base class model that provides activate and deactivate fields.
      """
      INACTIVE_STATUS, ACTIVE_STATUS = range(2)
      STATUS_CHOICES = (
          (INACTIVE_STATUS, _('Inactive')),
          (ACTIVE_STATUS, _('Active')),
      )
      status = models.IntegerField(_('status'), choices=STATUS_CHOICES,
          default=ACTIVE_STATUS)
      activate_date = models.DateTimeField(blank=True, null=True,
          help_text=_('keep empty for an immediate activation'))
      deactivate_date = models.DateTimeField(blank=True, null=True,
          help_text=_('keep empty for indefinite activation'))
      objects = ActivatorModelManager()
  
      class Meta:
          ordering = ('status', '-activate_date',)
          abstract = True
  
      def save(self, *args, **kwargs):
          if not self.activate_date:
              self.activate_date = datetime.datetime.now()
          super(ActivatorModel, self).save(*args, **kwargs)
  
new_contents: """
  Django Extensions abstract base model classes.
  """
  import datetime
  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:
          get_latest_by = 'modified'
          ordering = ('-modified', '-created',)
          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
  
  
  class ActivatorModelManager(models.Manager):
      """ ActivatorModelManager
      Manager to return instances of ActivatorModel: SomeModel.objects.active() / .inactive()
      """
      def active(self):
          """ Returns active instances of ActivatorModel: SomeModel.objects.active() """
          return self.get_query_set().filter(status=ActivatorModel.ACTIVE_STATUS)
  
      def inactive(self):
          """ Returns inactive instances of ActivatorModel: SomeModel.objects.inactive() """
          return self.get_query_set().filter(status=ActivatorModel.INACTIVE_STATUS)
  
  
  class ActivatorModel(models.Model):
      """ ActivatorModel
      An abstract base class model that provides activate and deactivate fields.
      """
      INACTIVE_STATUS, ACTIVE_STATUS = range(2)
      STATUS_CHOICES = (
          (INACTIVE_STATUS, _('Inactive')),
          (ACTIVE_STATUS, _('Active')),
      )
      status = models.IntegerField(_('status'), choices=STATUS_CHOICES,
          default=ACTIVE_STATUS)
      activate_date = models.DateTimeField(blank=True, null=True,
          help_text=_('keep empty for an immediate activation'))
      deactivate_date = models.DateTimeField(blank=True, null=True,
          help_text=_('keep empty for indefinite activation'))
      objects = ActivatorModelManager()
  
      class Meta:
          ordering = ('status', '-activate_date',)
          abstract = True
  
      def save(self, *args, **kwargs):
          if not self.activate_date:
              self.activate_date = datetime.datetime.now()
          super(ActivatorModel, self).save(*args, **kwargs)
  
subject: allow inheriting classes to modify ActivatorModelManager's `get_query_set()`