code: public ImmutableMap<Name, Long> snapshotModifiedTimes(JimfsPath path) throws IOException {
      ImmutableMap.Builder<Name, Long> modifiedTimes = ImmutableMap.builder();
  
      store.readLock().lock();
      try {
        Directory dir = (Directory) lookUp(path, Options.FOLLOW_LINKS).requireDirectory(path).file();
        // TODO(cgdecker): Investigate whether WatchServices should keep a reference to the actual
        // directory when SecureDirectoryStream is supported rather than looking up the directory
        // each time the WatchService polls
  
        for (DirectoryEntry entry : dir) {
          if (!entry.name().equals(Name.SELF) && !entry.name().equals(Name.PARENT)) {
            modifiedTimes.put(entry.name(), entry.file().getLastModifiedTime());
          }
        }
  
        return modifiedTimes.build();
      } finally {
        store.readLock().unlock();
      }
    }
docs: Returns a snapshot mapping the names of each file in the directory at the given path to the
  last modified time of that file.