code: def get_output_cache_key(self, placeholder_name, instance):
          
          cachekey = self.get_output_cache_base_key(placeholder_name, instance)
          if self.cache_output_per_site:
              cachekey = "{0}-s{1}".format(cachekey, settings.SITE_ID)
  
          # Append language code
          if self.cache_output_per_language:
              # NOTE: Not using self.language_code, but using the current language instead.
              #       That is what the {% trans %} tags are rendered as after all.
              #       The render_placeholder() code can switch the language if needed.
              user_language = get_language()
              if user_language not in self.cache_supported_language_codes:
                  user_language = 'unsupported'
              cachekey = "{0}.{1}".format(cachekey, user_language)
  
          return cachekey
docs: .. versionadded:: 0.9
             Return the default cache key which is used to store a rendered item.
             By default, this function generates the cache key using :func:`get_output_cache_base_key`.