code: private UserRegistryService getUserRegistryService(String id) {
          UserRegistryService service = userRegistry.getService(id);
          if (service == null) {
              throwIllegalArgumentExceptionInvalidAttributeValue(SecurityConfiguration.CFG_KEY_USERREGISTRY_REF, id);
          }
          return service;
      }
docs: Retrieve the UserRegistryService for the specified id.
  
  @param id UserRegistryService id to retrieve
  @return A non-null UserRegistryService instance.