code: function add(items) {
      var self = this;
      var children = self.get('children');
      if (Util.isArray(items)) {
        Util.each(items, function (item) {
          var parent = item.get('parent');
          if (parent) {
            parent.removeChild(item, false);
          }
          self._setCfgProperty(item);
        });
        self._cfg.children = children.concat(items);
      } else {
        var item = items;
        var parent = item.get('parent');
        if (parent) {
          parent.removeChild(item, false);
        }
        self._setCfgProperty(item);
        children.push(item);
      }
      return self;
    }
docs: 向组中添加shape或者group
  @param {Object} items 图形或者分组
  @return {Object} group 本尊