@Override
  public @NotNull Set<K> keySet() {
    final Set<K> ts = getMap().keySet();
    K nullKey = FAKE_NULL();
    if (ts.contains(nullKey)) {
      Set<K> hashSet = new HashSet<>(ts);
      hashSet.remove(nullKey);
      hashSet.add(null);
      return hashSet;
    }
    return ts;
  }
@Override
  public @NotNull Set<K> keySet()