code: def icon_cache_key(method, self, brain_or_object):
      
      url = api.get_url(brain_or_object)
      modified = api.get_modification_date(brain_or_object).millis()
      key = "{}?modified={}".format(url, modified)
      logger.debug("Generated Cache Key: {}".format(key))
      return key
docs: Generates a cache key for the icon lookup
  
      Includes the virtual URL to handle multiple HTTP/HTTPS domains
      Example: http://senaite.local/clients?modified=1512033263370