code: public static Multimap<Extract, WorkUnitState> createExtractToWorkUnitStateMap(
        Collection<? extends WorkUnitState> workUnitStates) {
      Multimap<Extract, WorkUnitState> extractToWorkUnitStateMap = ArrayListMultimap.create();
  
      for (WorkUnitState workUnitState : workUnitStates) {
        extractToWorkUnitStateMap.put(workUnitState.getExtract(), workUnitState);
      }
      return extractToWorkUnitStateMap;
    }
docs: Creates a {@link Multimap} that maps {@link Extract} to their corresponds {@link WorkUnitState}s.
  
  @see Multimap