code: public Map<String, Set<String>> getTargetLanguagesByBundle() {
          if (targetLanguagesByBundle == null) {
              assert false;
              return Collections.emptyMap();
          }
          return Collections.unmodifiableMap(targetLanguagesByBundle);
      }
docs: Returns the map containing target languages indexed by bundle IDs.
  This method always returns non-null map.
  
  @return  The map containing target languages indexed by bundle IDs.