@SuppressWarnings("unused") // called via reflection
  public static Runnable removeFileSystemRunnable(final URI uri) {
    return new Runnable() {
      @Override
      public void run() {
        fileSystems.remove(uri);
      }
    };
  }
Returns a runnable that, when run, removes the file system with the given URI from this
provider.
jimfs/src/main/java/com/google/common/jimfs/SystemJimfsFileSystemProvider.java