KOstache layout in a layout

gistfile1.php

<?php defined('SYSPATH') or die('No direct script access.');
/**
 * Mustache templates for Kohana.
 *
 * @package    Kostache
 * @category   Base
 * @author     Jeremy Bush <jeremy.bush@kohanaframework.org>
 * @author     Woody Gilk <woody.gilk@kohanaframework.org>
 * @copyright  (c) 2010-2011 Jeremy Bush
 * @copyright  (c) 2011 Woody Gilk
 * @license    MIT
 */
abstract class Kohana_Kostache_Layout extends Kostache {

	/**
	 * @var  string  partial name for content
	 */
	const CONTENT_PARTIAL = 'content';

	/**
	 * @var  boolean  render template in layout?
	 */
	public $render_layout = TRUE;

	/**
	 * @var  string  layout path
	 */
	protected static $_layout = 'layout';

	/**
	 *
	 */
	public function render($child_layout = NULL)
	{
		if ( ! $this->render_layout)
		{
			return parent::render();
		}

		$partials = $this->_partials;

		// is content partial a _template or child_layout
		$partial = (NULL == $child_layout) ? $this->_template : $child_layout;

		// add current template or child_layout as content partial
		$partials[Kostache_Layout::CONTENT_PARTIAL] = $partial;

		$template = $this->_load(static::$_layout);

		// if this layout is called 'layout', meaning outermost layout,
		// return output,
		// else pass this layout as child_layout to parent_layout
		if ('layout' == static::$_layout)
		{
			return $this->_stash($template, $this, $partials)->render();
		}
		else
		{
			$sub = $this->_stash($template, $this, $partials)->render();

			$parent_layout_class_name = static::$_parent_layout;
			$parent_layout_class = new $parent_layout_class_name();
			return $parent_layout_class->render($sub);
		}
	}
}

gistfile2.php

<?php defined('SYSPATH') or die('No direct script access.');

class View_Layout extends KOstache_Layout
{
	/**
	 * @var  string  layout path
	 */
	protected static $_layout = 'layout';
}

gistfile3.php

<?php defined('SYSPATH') or die('No direct script access.');

class View_Sub extends View_Layout
{
	/**
	 * @var  string  layout path
	 */
	protected static $_layout = 'sub';

	/**
	 * @var string 	layout will be set as partial in parent layout
	 */
	protected static $_parent_layout= 'View_Layout';
}