code: public void addLostStorage(String tierAlias, String dirPath) {
      List<String> paths = mLostStorage.getOrDefault(tierAlias, new ArrayList<>());
      paths.add(dirPath);
      mLostStorage.put(tierAlias, paths);
    }
docs: Adds a new worker lost storage path.
  
  @param tierAlias the tier alias
  @param dirPath the lost storage path