code: private WorkUnitState copyOf(WorkUnitState src) {
      WorkUnit copiedWorkUnit = WorkUnit.copyOf(src.getWorkunit());
      copiedWorkUnit.addAllIfNotExist(src.getJobState());
  
      WorkUnitState workUnitState = new WorkUnitState(copiedWorkUnit, src.getJobState());
      workUnitState.addAll(src);
      return workUnitState;
    }
docs: Copy WorkUnitState so that work unit also contains job state. FileBasedExtractor needs properties from job state (mostly source.* properties),
  where it has been already removed when reached here.
  
  @param src
  @return