public final void doesNotContainKey(@Nullable Object key) {
    check("keySet()").that(checkNotNull(actual).keySet()).doesNotContain(key);
  }
@Test
  public void doesNotContainKeyFailure() {
    ImmutableMap<String, String> actual = ImmutableMap.of("kurt", "kluever");
    expectFailureWhenTestingThat(actual).doesNotContainKey("kurt");
    assertFailureKeys("value of", "expected not to contain", "but was", "map was");
    assertFailureValue("value of", "map.keySet()");
    assertFailureValue("expected not to contain", "kurt");
    assertFailureValue("but was", "[kurt]");
  }