docs: def published(self, request=None):
          """
          Returns the published documents in the current language.
  
          :param request: A Request instance.
  
          """
          language = getattr(request, 'LANGUAGE_CODE', get_language())
          if not language:
              return self.model.objects.none()
  
          qs = self.get_queryset()
          qs = qs.filter(
              translations__is_published=True,
              translations__language_code=language,
          )
          # either it has no category or the one it has is published
          qs = qs.filter(
              models.Q(category__isnull=True) |
              models.Q(category__is_published=True))
          return qs