code: public Observable<ServiceResponse<DomainInner>> beginUpdateWithServiceResponseAsync(String resourceGroupName, String domainName) {
          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 (domainName == null) {
              throw new IllegalArgumentException("Parameter domainName is required and cannot be null.");
          }
          if (this.client.apiVersion() == null) {
              throw new IllegalArgumentException("Parameter this.client.apiVersion() is required and cannot be null.");
          }
          final Map<String, String> tags = null;
          DomainUpdateParameters domainUpdateParameters = new DomainUpdateParameters();
          domainUpdateParameters.withTags(null);
          return service.beginUpdate(this.client.subscriptionId(), resourceGroupName, domainName, this.client.apiVersion(), this.client.acceptLanguage(), domainUpdateParameters, this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<DomainInner>>>() {
                  @Override
                  public Observable<ServiceResponse<DomainInner>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<DomainInner> clientResponse = beginUpdateDelegate(response);
                          return Observable.just(clientResponse);
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Update a domain.
  Asynchronously updates a domain with the specified parameters.
  
  @param resourceGroupName The name of the resource group within the user's subscription.
  @param domainName Name of the domain
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the DomainInner object