@Test
void testFilterByKeys() {

    ImmutableMap<String, Integer> toFilter = ImmutableMap.of(
            "A", 1,
            "B", 2,
            "C", 3,
            "D", 4);
    ImmutableMap<String, Integer> expected = ImmutableMap.of(
            "B", 2,
            "C", 3,
            "D", 4);
    ImmutableMap<String, Integer> actual = ImmutableMapFactory.filterByKeys(toFilter, key -> !key.equals("A"));
    Assertions.assertEquals(expected, actual);
}