* by applying the given {@code AsyncFunction} to the result of the original {@code Future}.
   * Example usage:
   *
   * <pre>{@code
   * FluentFuture<RowKey> rowKeyFuture = FluentFuture.from(indexService.lookUp(query));
   * ListenableFuture<QueryResult> queryFuture =
   *     rowKeyFuture.transformAsync(dataService::readFuture, executor);
   * }</pre>
   *