public static function getFormats() : array
    {
        return [
            self::FORMAT_GSM => self::FORMAT_GSM,
            self::FORMAT_UNICODE => self::FORMAT_UNICODE,
            self::FORMAT_BINARY => self::FORMAT_BINARY,
            self::FORMAT_WAPPUSH => self::FORMAT_WAPPUSH,
            self::FORMAT_MMS => self::FORMAT_MMS
        ];
    }