code: public Observable<CheckAvailabilityResultInner> checkNotificationHubAvailabilityAsync(String resourceGroupName, String namespaceName, CheckAvailabilityParameters parameters) {
          return checkNotificationHubAvailabilityWithServiceResponseAsync(resourceGroupName, namespaceName, parameters).map(new Func1<ServiceResponse<CheckAvailabilityResultInner>, CheckAvailabilityResultInner>() {
              @Override
              public CheckAvailabilityResultInner call(ServiceResponse<CheckAvailabilityResultInner> response) {
                  return response.body();
              }
          });
      }
docs: Checks the availability of the given notificationHub in a namespace.
  
  @param resourceGroupName The name of the resource group.
  @param namespaceName The namespace name.
  @param parameters The notificationHub name.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the CheckAvailabilityResultInner object