code: public Observable<DataMigrationServiceInner> getByResourceGroupAsync(String groupName, String serviceName) {
          return getByResourceGroupWithServiceResponseAsync(groupName, serviceName).map(new Func1<ServiceResponse<DataMigrationServiceInner>, DataMigrationServiceInner>() {
              @Override
              public DataMigrationServiceInner call(ServiceResponse<DataMigrationServiceInner> response) {
                  return response.body();
              }
          });
      }
docs: Get DMS Service Instance.
  The services resource is the top-level resource that represents the Data Migration Service. The GET method retrieves information about a service instance.
  
  @param groupName Name of the resource group
  @param serviceName Name of the service
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the DataMigrationServiceInner object