Class namespace issue if package installed in a parent directory

[diamond-fish]

Problem description:

How do I reference the use statements if selling-partner-api is installed in a parent directory?

I'm trying the quickstart code but it's not working.

Error:

PHP Fatal error:  Uncaught Error: Class "SellingPartnerApi\Endpoint" not found

Code

require_once(__DIR__ . '../../../../../../vendor/autoload.php');

use SellingPartnerApi\Api\SellersV1Api as SellersApi;
use SellingPartnerApi\Configuration;
use SellingPartnerApi\Endpoint;

$config = new Configuration(...);