code: public function getSubscription($subscriptionRequest)
      {
          if (is_array($subscriptionRequest)) {
              $subscriptionRequest = RequestCreator::create(GetSubscriptionRequest::class, $subscriptionRequest);
          } else if (!($subscriptionRequest instanceof GetSubscriptionRequest)) {
              $subscriptionRequest = new GetSubscriptionRequest($subscriptionRequest);
          }
  
          ObjectRecursiveValidator::validate($subscriptionRequest);
          $serializer = new GetSubscriptionSerializer($subscriptionRequest);
          $transport = new GetSubscriptionTransport($serializer);
  
          return $this->execute($transport, GetSubscriptionResponse::class);
      }
docs: @param array|GetSubscriptionRequest $subscriptionRequest
  
  @return AbstractResponse|GetSubscriptionResponse
  @throws ResponseException
  @throws TransportException