code: @Override
  	public <T> T doWithRest(RestOperationsCallback<T> callback) {
  		Assert.notNull(callback, "callback must not be null");
  
  		try {
  			return callback.doWithRestOperations(restTemplate);
  		}
  		catch (HttpStatusCodeException e) {
  			throw new CredHubException(e);
  		}
  	}
docs: Allow interaction with the configured {@link RestTemplate} not provided
  by other methods.
  
  @param callback wrapper for the callback method
  @param <T> the credential implementation type
  @return the return value from the callback method