code: function(key, args, fallbackString) {
              var index = key.lastIndexOf(".");
              var prop = gTextProp;
              if (index > 0) {
                  // An attribute has been specified
                  prop = key.substr(index + 1);
                  key = key.substring(0, index);
              }
              var fallback;
              if (fallbackString) {
                  fallback = {};
                  fallback[prop] = fallbackString;
              }
              var data = getL10nData(key, args, fallback);
              if (data && prop in data) {
                  return data[prop];
              }
              return "{{" + key + "}}";
          }
docs: get a localized string