code: public ServiceFuture<TopicInner> getByResourceGroupAsync(String resourceGroupName, String topicName, final ServiceCallback<TopicInner> serviceCallback) {
          return ServiceFuture.fromResponse(getByResourceGroupWithServiceResponseAsync(resourceGroupName, topicName), serviceCallback);
      }
docs: Get a topic.
  Get properties of a topic.
  
  @param resourceGroupName The name of the resource group within the user's subscription.
  @param topicName Name of the topic
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object