code: private static Multimap<CopyEntity.DatasetAndPartition, WorkUnitState> groupByFileSet(
        Collection<? extends WorkUnitState> states) {
      Multimap<CopyEntity.DatasetAndPartition, WorkUnitState> datasetRoots = ArrayListMultimap.create();
  
      for (WorkUnitState workUnitState : states) {
        CopyEntity file = CopySource.deserializeCopyEntity(workUnitState);
        CopyEntity.DatasetAndPartition datasetAndPartition = file.getDatasetAndPartition(
            CopyableDatasetMetadata.deserialize(workUnitState.getProp(CopySource.SERIALIZED_COPYABLE_DATASET)));
  
        datasetRoots.put(datasetAndPartition, workUnitState);
      }
      return datasetRoots;
    }
docs: Create a {@link Multimap} that maps a {@link CopyableDataset} to all {@link WorkUnitState}s that belong to this
  {@link CopyableDataset}. This mapping is used to set WorkingState of all {@link WorkUnitState}s to
  {@link WorkUnitState.WorkingState#COMMITTED} after a {@link CopyableDataset} is successfully published.