code: protected File getStoreFile(StoreReference store)
      {
          if (store instanceof FileStoreReference) {
              return ((FileStoreReference) store).getFile();
          }
          throw new IllegalArgumentException(String.format("Unsupported store reference [%s] for this implementation.",
              store.getClass().getName()));
      }
docs: Return the file corresponding to the given store reference.
  
  @param store the store reference.
  @return a file or folder for storage.
  @throws java.lang.IllegalArgumentException if the reference is not appropriate for a filesystem storage.