code: public Observable<Void> beginDeleteAsync(String resourceGroupName, String registryName, String buildTaskName) {
          return beginDeleteWithServiceResponseAsync(resourceGroupName, registryName, buildTaskName).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Deletes a specified build task.
  
  @param resourceGroupName The name of the resource group to which the container registry belongs.
  @param registryName The name of the container registry.
  @param buildTaskName The name of the container registry build task.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponse} object if successful.