code: function (selector, context) {
              var all = Node.all(selector, context);
              return all.length ? all.slice(0, 1) : null;
          }
docs: Get node list with length of one
  from selector or construct new node list from html string.
  @param {String|KISSY.Node} selector Selector string or html string or common dom node.
  @param {String|KISSY.Node} [context] Search context for selector
  @return {KISSY.Node}
  @member KISSY.Node
  @static