code: def expire_cache(fragment_name, *args):
      
      cache_key = make_template_fragment_key(fragment_name, args)
      cache.delete(cache_key)
docs: Expire a cache item.
      
      @param url: The url object
      @param product_names: A list of product names
      @param start: The date from which the reporting should start.
      @param stop: The date at which the reporting should stop.