public static <K> Keys<K> create() {
    return new Keys<>();
  }
@Test
  @Category(ValidatesRunner.class)
  public void testKeysEmpty() {
    PCollection<KV<String, Integer>> input =
        p.apply(
            Create.of(Arrays.asList(EMPTY_TABLE))
                .withCoder(KvCoder.of(StringUtf8Coder.of(), BigEndianIntegerCoder.of())));

    PCollection<String> output = input.apply(Keys.create());
    PAssert.that(output).empty();
    p.run();
  }