public static MatchesKV matchesKV(String regex, int keyGroup, int valueGroup) {
    return matchesKV(Pattern.compile(regex), keyGroup, valueGroup);
  }
@Test
  @Category(NeedsRunner.class)
  public void testKVMatchesNone() {

    PCollection<KV<String, String>> output =
        p.apply(Create.of("x y z")).apply(Regex.matchesKV("a (b) (c)", 1, 2));
    PAssert.that(output).empty();
    p.run();
  }