code: public Observable<CertificateListDescriptionInner> listByIotHubAsync(String resourceGroupName, String resourceName) {
          return listByIotHubWithServiceResponseAsync(resourceGroupName, resourceName).map(new Func1<ServiceResponse<CertificateListDescriptionInner>, CertificateListDescriptionInner>() {
              @Override
              public CertificateListDescriptionInner call(ServiceResponse<CertificateListDescriptionInner> response) {
                  return response.body();
              }
          });
      }
docs: Get the certificate list.
  Returns the list of certificates.
  
  @param resourceGroupName The name of the resource group that contains the IoT hub.
  @param resourceName The name of the IoT hub.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the CertificateListDescriptionInner object