@Override
  @Nullable
  public V put(@Nullable K key, @Nullable V value) {
    return put(key, value, true);
  }
@Test
  void shouldContainValue() {
    assertFalse(this.map.containsValue("123"));
    assertFalse(this.map.containsValue(null));
    this.map.put(123, "123");
    this.map.put(456, null);
    assertTrue(this.map.containsValue("123"));
    assertTrue(this.map.containsValue(null));
  }