code: public static <T> Stream<T> concat(final Iterable<? extends Iterable<? extends T>> iterables) {
          return new ConcatStream<Iterable<? extends T>, T>(create(iterables));
      }
docs: Returns a Stream concatenating zero or more Iterables. If an input Iterable is a Stream, it
  is closed as soon as exhausted or as iteration completes.
  
  @param iterables
  an Iterable with the Iterables or Streams to concatenate
  @param <T>
  the type of elements
  @return the resulting concatenated Stream