code: public Observable<Void> beginStopAsync(String groupName, String serviceName) {
          return beginStopWithServiceResponseAsync(groupName, serviceName).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Stop service.
  The services resource is the top-level resource that represents the Data Migration Service. This action stops the service and the service cannot be used for data migration. The service owner won't be billed when the service is stopped.
  
  @param groupName Name of the resource group
  @param serviceName Name of the service
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponse} object if successful.