Laravel-excel: [BUG] Documentation mistake for ImportHandler?

Laravel-Excel:2.1.7 / Laravel: 5.3.24

In the docs under Import Handlers it states that the handle() function accepts/injects and instance of the Importer class but this not correct if you try and define it that way as the parameter cannot the typehinted:

Declaration of App\ExcelImporters\ContactsImporterHandler::handle() must be compatible with Maatwebsite\Excel\Files\ImportHandler::handle($file)

use Maatwebsite\Excel\Files\ImportHandler;
use App\ExcelImporters\ContactsImporter;

class ContactsImporterHandler implements ImportHandler
{
    public function handle(ContactsImporter $import)
    {
      ...
    }

Is this a mistake in the docs or something I've done wrong?