* An operation that computes a result.
   *
   * @param <V> the type of the result
   */
  public interface ClosingCallable<V extends @Nullable Object> {
    /**
     * Computes a result, or throws an exception if unable to do so.
     *
     * <p>Any objects that are passed to {@link DeferredCloser#eventuallyClose(Object, Executor)
     * closer.eventuallyClose()} will be closed when the {@link ClosingFuture} pipeline is done (but