code: <T, U> Stage<U> doStreamCollectEmpty(
        final Consumer<? super T> consumer, final Supplier<? extends U> supplier
    ) {
      try {
        return this.completed(supplier.get());
      } catch (Exception e) {
        return failed(e);
      }
    }
docs: Shortcut for when the list of stages is empty with stream collector.
  
  @param consumer consumer to apply
  @param supplier supplier to provide result
  @param <T> source type
  @param <U> target type