public static <T> Values<T> of(Iterable<T> elems) {
    return new Values<>(elems, Optional.absent(), Optional.absent(), false);
  }
@Test
  public void testSourceSplitVoid() throws Exception {
    CreateSource<Void> source =
        CreateSource.fromIterable(Lists.newArrayList(null, null, null, null, null), VoidCoder.of());
    PipelineOptions options = PipelineOptionsFactory.create();
    List<? extends BoundedSource<Void>> splitSources = source.split(3, options);
    SourceTestUtils.assertSourcesEqualReferenceSource(source, splitSources, options);
  }