code: function backgroundRefresh(){
      for(key in refreshKeys){
        if(refreshKeys.hasOwnProperty(key)){
          var data = refreshKeys[key];
          if(data.expiration - Date.now() < self.backgroundRefreshMinTtl){
            data.refresh(key, function (err, response){
              if(!err){
                self.set(key, response, data.lifeSpan, data.refresh, noop);
              }
            });
          }
        }
      }
    }
docs: Refreshes all keys that were set with a refresh function