Missing return type for SoapClientAuth::__doRequest (PHP 8.1.x)

[ReneGercken]

please add the return type "?string" for the method SoapClientAuth::__doRequest
because it leads to an error like

Deprecated: Return type of Thybag\Auth\SoapClientAuth::__doRequest($request, $location, $action, $version, $one_way = 0)
should either be compatible with SoapClient::__doRequest(string $request, string $location, string $action, int $version, bool $oneWay = false): ?string,
or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in ~\vendor\thybag\php-sharepoint-lists-api\src\Thybag\Auth\SoapClientAuth.php on line 84

public function __doRequest($request, $location, $action, $version, $one_way = 0):?string