code: function _$set(kp, value, lazyEmit) {
          if (_destroy) return _destroyNotice()
  
          return _$sync(kp, value, lazyEmit)
          // if (!diff) return
          /**
           *  Base type change of object type will be trigger change event
           *  next and pre value are not keypath value but property value
           */
          // if ( kp == diff.mounted && $util.diff(diff.next, diff.pre) ) {
          //     var propname = diff.mounted
          //     // emit change immediately
          //     _emitChange(propname, diff.next, diff.pre)
          // }
      }
docs: sync props value and trigger change event
  @param kp <String> keyPath