code: public Observable<ServiceResponse<TopicInner>> createOrUpdateWithServiceResponseAsync(String resourceGroupName, String topicName, TopicInner topicInfo) {
          if (this.client.subscriptionId() == null) {
              throw new IllegalArgumentException("Parameter this.client.subscriptionId() is required and cannot be null.");
          }
          if (resourceGroupName == null) {
              throw new IllegalArgumentException("Parameter resourceGroupName is required and cannot be null.");
          }
          if (topicName == null) {
              throw new IllegalArgumentException("Parameter topicName is required and cannot be null.");
          }
          if (topicInfo == null) {
              throw new IllegalArgumentException("Parameter topicInfo is required and cannot be null.");
          }
          if (this.client.apiVersion() == null) {
              throw new IllegalArgumentException("Parameter this.client.apiVersion() is required and cannot be null.");
          }
          Validator.validate(topicInfo);
          Observable<Response<ResponseBody>> observable = service.createOrUpdate(this.client.subscriptionId(), resourceGroupName, topicName, topicInfo, this.client.apiVersion(), this.client.acceptLanguage(), this.client.userAgent());
          return client.getAzureClient().getPutOrPatchResultAsync(observable, new TypeToken<TopicInner>() { }.getType());
      }
docs: Create a topic.
  Asynchronously creates a new topic with the specified parameters.
  
  @param resourceGroupName The name of the resource group within the user's subscription.
  @param topicName Name of the topic
  @param topicInfo Topic information
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable for the request