docs: def get_next_slug(self, slug, **kwargs):
          """Gets the next available slug.
  
          :param slug: the slug to slugify
          :param kwargs: additional filter criteria to check for when looking for
              a unique slug.
  
          Example:
  
          if the value "my-slug" is already taken, this method will append "-n"
          to the end of the slug until the next available slug is found.
  
          """
          original_slug = slug = slugify(slug)
          count = 0
  
          while not self.is_slug_available(slug=slug, **kwargs):
              count += 1
              slug = '{0}-{1}'.format(original_slug, count)
  
          return slug