docs: public static <T, U> DictionaryFeatureVectorGenerator<T, U> createFromData(Collection<T> data,
        FeatureGenerator<T, U> generator, boolean ignoreOovFeatures) {
      IndexedList<U> features = new IndexedList<U>();
      for (T datum : data) {
        features.addAll(generator.generateFeatures(datum).keySet());
      }
      return new DictionaryFeatureVectorGenerator<T, U>(features, generator, ignoreOovFeatures);
    }