@NotNull
  public List<FacetInfo> getChildren(@Nullable FacetInfo info) {
    final List<FacetInfo> list = myParents.getKeysByValue(null2Root(info));
    if (list == null) {
      return Collections.emptyList();
    }
    return Collections.unmodifiableList(list);
  }
@NotNull
  public List<FacetInfo> getChildren(@Nullable FacetInfo info)