code: def clean_slug(self):
          
          source = self.cleaned_data.get('slug', '')
          lang_choice = self.language_code
          if not source:
              source = slugify(self.cleaned_data.get('title', ''))
          qs = Post._default_manager.active_translations(lang_choice).language(lang_choice)
          used = list(qs.values_list('translations__slug', flat=True))
          slug = source
          i = 1
          while slug in used:
              slug = '%s-%s' % (source, i)
              i += 1
          return slug
docs: Generate a valid slug, in case the given one is taken