code: function backgroundRefresh() {
      var keys = Object.keys(refreshKeys);
      keys.forEach(function(key) {
        var data = refreshKeys[key];
        if(data.expiration - Date.now() < this.backgroundRefreshMinTtl){
          data.refresh(key, handleRefreshResponse.bind(this, key, data));
        }
      }, self);
    }
docs: Refreshes all keys that were set with a refresh function