code: public CompletableFuture<SubscriptionDescription> getSubscriptionAsync(String topicPath, String subscriptionName) {
          EntityNameHelper.checkValidTopicName(topicPath);
          EntityNameHelper.checkValidSubscriptionName(subscriptionName);
  
          String path = EntityNameHelper.formatSubscriptionPath(topicPath, subscriptionName);
          CompletableFuture<String> contentFuture = getEntityAsync(path, null, false);
          CompletableFuture<SubscriptionDescription> sdFuture = new CompletableFuture<>();
          contentFuture.handleAsync((content, ex) -> {
              if (ex != null) {
                  sdFuture.completeExceptionally(ex);
              } else {
                  try {
                      sdFuture.complete(SubscriptionDescriptionSerializer.parseFromContent(topicPath, content));
                  } catch (MessagingEntityNotFoundException e) {
                      sdFuture.completeExceptionally(e);
                  }
              }
              return null;
          }, MessagingFactory.INTERNAL_THREAD_POOL);
  
          return sdFuture;
      }
docs: Retrieves a subscription for a given topic from the service namespace
  @param topicPath - The path of the topic relative to service bus namespace.
  @param subscriptionName - The name of the subscription
  @return - SubscriptionDescription containing information about the subscription.
  @throws IllegalArgumentException - Thrown if path is null, empty, or not in right format or length.