@Override
  @NotNull
  public final Map<Key<?>, Object> exportUserData() {
    Map<Key<?>, Object> result = new HashMap<>();
    KeyFMap map = getUserMap();
    for (Key<?> k : map.getKeys()) {
      final Object data = map.get(k);
      if (data != null) {
        result.put(k, data);
      }
    }
    return result;
  }
@Override
  @NotNull
  public final Map<Key<?>, Object> exportUserData()