Vendor files load

I have problem with Paylane rest client and Cakephp 3. Via console and composer I download Paylane rest client:

https://packagist.org/packages/paylane/client

composer require paylane/client
Ok, now I try to call this class.

require_once(ROOT .DS. 'vendor' . DS  . 'paylane' . DS . 'client' . DS . 'paylane' . DS . 'PayLaneRestClient.php');
$client = new PayLaneRestClient('aaaaa', 'aaaaaa');

But I still have error:

Call to undefined function Controller\PayLaneRestClient()

How I can resolve this ?

You do not have to use require as all vendor files are autoloaded.

Instead of this you should call use PayLaneRestClient; at the begginning of your controller (where the other use calls are).