/**
  * 
  * @param string $shortcode
  * @return \WordPress\ShortCodeTree
  */
 public static function fromString($shortcode)
 {
     $tree = new ShortcodeTree();
     $nodes = Shortcode::fromString($shortcode);
     if (count($nodes)) {
         if (count($nodes) > 1) {
             $root = new Shortcode();
             foreach ($nodes as $node) {
                 $root->add_shortcode($node);
             }
             $tree->setRoot($root);
         } else {
             $tree->setRoot($nodes[0]);
         }
     }
     return $tree;
 }