@Override
  @Nullable
  public V put(@Nullable K key, @Nullable V value) {
    return put(key, value, true);
  }
@Test
  void shouldGetValues() {
    this.map.put(123, "123");
    this.map.put(456, null);
    this.map.put(null, "789");
    List<String> actual = new ArrayList<>(this.map.values());
    List<String> expected = new ArrayList<>();
    expected.add("123");
    expected.add(null);
    expected.add("789");
    actual.sort(NULL_SAFE_STRING_SORT);
    expected.sort(NULL_SAFE_STRING_SORT);
    assertThat(actual, equalTo(expected));
  }