protected function parseGroupOpen(Token\Group\Open $token, \SplStack $stack) 
	{
		$group = new Element\Group();
		
		// if the group is not the root
		if ($stack->count() > 0) {
			// set the parent-child and child-parent relationships
			$group->setParent($stack->top());
			$stack->top()->appendChild($group);
		}
		
		$stack->push($group);
		
		return;
	}