public function uniqueAliases(string $string) : array
    {
        $return = [];
        foreach (preg_split('//u', $string, -1, PREG_SPLIT_NO_EMPTY) as $char) {
            $alias = $this->alias($char);
            if (! in_array($alias, $return)) {
                array_push($return, $alias);
            }
        }
        return $return;
    }