code: def _clean_page_automatic_slug_renaming(self, slug, is_slug_safe):
          
  
          if not callable(is_slug_safe):
              raise TypeError('is_slug_safe must be callable')
  
          if is_slug_safe(slug):
              return slug
  
          count = 2
          new_slug = slug + "-" + str(count)
          while not is_slug_safe(new_slug):
              count = count + 1
              new_slug = slug + "-" + str(count)
          return new_slug
docs: Helper to add numbers to slugs