code: public Set<Feature> getFeature(FeatureEnum feature)
    {
      return ImmutableSet.copyOf(features.get(feature));
    }
docs: Returns the set of {@link Feature} stored in this report for the given
  feature name.
  
  @param feature
  the feature name to look-up
  @return the (possibly empty) set of {@link Feature} stored in this report
  for the given feature name.