code: public static <A, B, C> FeatureGenerator<A, C> postConvertingFeatureGenerator(
        FeatureGenerator<A, B> generator, Function<B, C> converter) {
      return new PostConvertingFeatureGenerator<A, B, C>(generator, converter);
    }
docs: Gets a feature generator that applies a generator, then
  applies a converter to the generated feature names.
  
  @param generator
  @param converter
  @return