code: public Observable<ServiceResponse<Void>> addUsersWithServiceResponseAsync(String resourceGroupName, String labAccountName, String labName, List<String> emailAddresses) {
          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 (labAccountName == null) {
              throw new IllegalArgumentException("Parameter labAccountName is required and cannot be null.");
          }
          if (labName == null) {
              throw new IllegalArgumentException("Parameter labName is required and cannot be null.");
          }
          if (this.client.apiVersion() == null) {
              throw new IllegalArgumentException("Parameter this.client.apiVersion() is required and cannot be null.");
          }
          if (emailAddresses == null) {
              throw new IllegalArgumentException("Parameter emailAddresses is required and cannot be null.");
          }
          Validator.validate(emailAddresses);
          AddUsersPayload addUsersPayload = new AddUsersPayload();
          addUsersPayload.withEmailAddresses(emailAddresses);
          return service.addUsers(this.client.subscriptionId(), resourceGroupName, labAccountName, labName, this.client.apiVersion(), this.client.acceptLanguage(), addUsersPayload, this.client.userAgent())
              .flatMap(new Func1<Response<ResponseBody>, Observable<ServiceResponse<Void>>>() {
                  @Override
                  public Observable<ServiceResponse<Void>> call(Response<ResponseBody> response) {
                      try {
                          ServiceResponse<Void> clientResponse = addUsersDelegate(response);
                          return Observable.just(clientResponse);
                      } catch (Throwable t) {
                          return Observable.error(t);
                      }
                  }
              });
      }
docs: Add users to a lab.
  
  @param resourceGroupName The name of the resource group.
  @param labAccountName The name of the lab Account.
  @param labName The name of the lab.
  @param emailAddresses List of user emails addresses to add to the lab.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponse} object if successful.