private static function findUnsavedChildren(
        $object,
        &$unsavedChildren,
        &$unsavedFiles
    ) {
        static::traverse(true, $object, function ($obj) use (
            &$unsavedChildren,
            &$unsavedFiles
        )
        {
            if ($obj instanceof AVObject)
            {
                if ($obj->_isDirty(false))
                {
                    $unsavedChildren[] = $obj;
                }
            } else if ($obj instanceof AVFile)
            {
                if (!$obj->getURL())
                {
                    $unsavedFiles[] = $obj;
                }
            }

        });
    }