code: def is_valid_article_slug(article, language, slug):
      
      from ..models import Title
  
      qs = Title.objects.filter(slug=slug, language=language)
  
      if article.pk:
          qs = qs.exclude(Q(language=language) & Q(article=article))
          qs = qs.exclude(article__publisher_public=article)
  
      if qs.count():
          return False
  
      return True
docs: Validates given slug depending on settings.