code: public Observable<Boolean> checkExistenceAsync(String resourceGroupName) {
          return checkExistenceWithServiceResponseAsync(resourceGroupName).map(new Func1<ServiceResponse<Boolean>, Boolean>() {
              @Override
              public Boolean call(ServiceResponse<Boolean> response) {
                  return response.body();
              }
          });
      }
docs: Checks whether a resource group exists.
  
  @param resourceGroupName The name of the resource group to check. The name is case insensitive.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the Boolean object