code: public Observable<Void> addUsersAsync(String resourceGroupName, String labAccountName, String labName, List<String> emailAddresses) {
          return addUsersWithServiceResponseAsync(resourceGroupName, labAccountName, labName, emailAddresses).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
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.