@SafeVarargs
  public static <InputT> Builders.Output<InputT> of(PCollection<InputT>... pCollections) {
    return of(Arrays.asList(pCollections));
  }
@Test
  public void testBuild_ImplicitName() {
    final TestPipeline pipeline = TestUtils.createTestPipeline();
    final PCollection<String> left =
        TestUtils.createMockDataset(pipeline, TypeDescriptors.strings());
    final PCollection<String> right =
        TestUtils.createMockDataset(pipeline, TypeDescriptors.strings());
    final PCollection<String> unioned = Union.of(left, right).output();
    final Union union = (Union) TestUtils.getProducer(unioned);
    assertFalse(union.getName().isPresent());
  }