code: function (type) {
              if (typeof type === 'string') {
                  type = zn.path(GLOBAL, type);
              }
  
              if (type) {
                  if (this instanceof type) {
                      return true;
                  } else {
                      var _mixins = this.constructor._mixins_;
                      for (var i = 0, _len = _mixins.length; i < _len; i++) {
                          var _mixin = _mixins[i];
                          if (type === _mixin) {
                              return true;
                          }
                      }
                  }
              }
  
              return false;
          }
docs: Check whether current object is specified type.
  @method is
  @param type {String|Function}
  @returns {Boolean}