code: public Observable<List<PrebuiltDomain>> listAvailableCustomPrebuiltDomainsAsync() {
          return listAvailableCustomPrebuiltDomainsWithServiceResponseAsync().map(new Func1<ServiceResponse<List<PrebuiltDomain>>, List<PrebuiltDomain>>() {
              @Override
              public List<PrebuiltDomain> call(ServiceResponse<List<PrebuiltDomain>> response) {
                  return response.body();
              }
          });
      }
docs: Gets all the available custom prebuilt domains for all cultures.
  
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;PrebuiltDomain&gt; object