public final void isNotEmpty() {
    if (checkNotNull(actual).isEmpty()) {
      failWithoutActual(simpleFact("expected not to be empty"));
    }
  }
@Test
  public void isNotEmptyWithFailure() {
    ImmutableMap<Integer, Integer> actual = ImmutableMap.of();
    expectFailureWhenTestingThat(actual).isNotEmpty();
    assertFailureKeys("expected not to be empty");
  }