code: function () {
        var this$1 = this;
  
        // the context of `this` will be equal to riot tag instant.
        this.on('unmount', function () {
          this$1.off('*');
          forEach_1(this$1._riotx_change_handlers, function (obj) {
            obj.store.off(obj.evtName, obj.handler);
          });
          delete this$1.riotx;
          delete this$1._riotx_change_handlers;
          delete this$1[settings.changeBindName];
        });
  
        if (settings.debug) {
          this.on('*', function (eventName) {
            debug('[riot.mixin]', eventName, this$1);
          });
        }
  
        this._riotx_change_handlers = [];
  
        // let users set the name.
        this[settings.changeBindName] = riotxChange;
      }
docs: intendedly use `function`. switch the context of `this` from `riotx` to `riot tag instance`.