code: def object_version_choices(obj):
      
      choices = BLANK_CHOICE_DASH + [(PublishAction.UNPUBLISH_CHOICE, 'Unpublish current version')]
  
      # When creating a new object in the Django admin - obj will be None
      if obj is not None:
          saved_versions = Version.objects.filter(
              content_type=ContentType.objects.get_for_model(obj),
              object_id=obj.pk,
          ).exclude(
              version_number=None,
          )
  
          for version in saved_versions:
              choices.append((version.version_number, version))
  
      return choices
docs: Return a list of form choices for versions of this object which can be published.