code: function (event) {
              // duplicate,in case detach itself in one observer
              var observers = [].concat(this.observers), ret, gRet, len = observers.length, i;
              for (i = 0; i < len && !event.isImmediatePropagationStopped(); i++) {
                  ret = observers[i].notify(event, this);
                  if (gRet !== false && ret !== undefined) {
                      gRet = ret;
                  }
              }
              return gRet;
          }
docs: notify current event 's observers
  @param {KISSY.Event.CustomEvent.Object} event
  @return {*} return false if one of custom event 's observers  else
  return last value of custom event 's observers 's return value.