code: def make_unpublished(self, request, queryset):
          
          updates = queryset.filter(publish=True)\
              .update(publish=False)
          messages.add_message(
              request, messages.INFO,
              __('%(updates)d entry unpublished.',
                  '%(updates)d entries unpublished.', updates) % {
                  'updates':  updates, })
docs: Bulk action to mark selected posts as UNpublished.
              queryset must not be empty (ensured by DjangoCMS).