code: function (observer) {
              var self = this, i, observers = self.observers, len = observers.length;
              for (i = 0; i < len; i++) {
                  if (observers[i] === observer) {
                      observers.splice(i, 1);
                      break;
                  }
              }
              self.checkMemory();
          }
docs: remove one observer from current event's observers
  @param {KISSY.Event.Observer} observer