code: function wrap($node, $wrap_index = -1, $node_index = null) {
  		if ($node_index === null) {
  			$node_index = $this->index();
  		}
  
  		if (!is_object($node)) {
  			$node = $this->parent->addChild($node, $node_index);
  		} elseif ($node->parent !== $this->parent) {
  			$node->changeParent($this->parent, $node_index);
  		}
  
  		$this->changeParent($node, $wrap_index);
  		return $node;
  	}
docs: Wrap node
  @param string|DomNode $node Wrapping node, string to create new element node
  @param int $wrap_index Index to insert current node in wrapping node, -1 to append
  @param int $node_index Index to insert wrapping node, null to keep at same position
  @return DomNode Wrapping node