private function validateAddingChildren(NodeInterface $parentNode)
	{
		$allow = true;
		
		/*
		 * FIXME: These checks are not good, but we can receive NodeAbstraction
		 * or other NodeInterface with magic __call as well..
		 */
		if ($parentNode instanceof NodeAbstraction) {
			if ($parentNode->leafInterface) {
				$allow = false;
			}
		}
		
		if ($parentNode instanceof NodeLeafInterface) {
			$allow = false;
		}
		
		if ( ! $allow) {
			$parentDump = static::dump($parentNode);
			throw new Exception\InvalidOperation("Children cannot added to the NodeLeafInterface object {$parentDump}");
		}
	}