code: public static <T extends Configuration<T>, U extends ValidationProvider<T>> //
        ProviderSpecificBootstrap<T> //
        byProvider(final Class<U> providerType) {
      throw new UnsupportedOperationException(
          "GWT Validation does not support custom validator " + "providers");
    }
docs: Unsupported. Always throws an {@link UnsupportedOperationException}.
  
  @param <T> configuration type
  @param <U> validation provider type
  
  @param providerType class of the provider type
  @return provider specific bootstrap
  
  @throws UnsupportedOperationException not supported