public function getAllKeys()
    {

        // initialize the array with keys of all attributes
        $keys = array();

        // prepare the pattern to filter the attributes
        $pattern = sprintf('%s-*', $this->getSerial());

        // prepare the array with the attribute keys
        foreach (array_keys((array) $this) as $key) {
            if (fnmatch($pattern, $key)) {
                $keys[] = $this->unmaskKey($key);
            }
        }

        // return the attribute keys
        return $keys;
    }