code: function (selector) {
              var self = this, all = self.all(selector), ret = all.length ? all.slice(0, 1) : null;
              if (ret) {
                  ret.__parent = self;
              }
              return ret;
          }
docs: Get node list which match selector under current node list sub tree.
  @param {String} selector
  @return {KISSY.Node}