@Override
  public @Nullable String getGroupName(final @NotNull RefElement entity) {
    for (RefManagerExtension<?> extension : myExtensions.values()) {
      final String groupName = extension.getGroupName(entity);
      if (groupName != null) return groupName;
    }

    RefEntity parent = entity.getOwner();
    while (parent != null && !(parent instanceof RefDirectory)) {
      parent = parent.getOwner();
    }
    final LinkedList<String> containingDirs = new LinkedList<>();
    while (parent instanceof RefDirectory) {
      containingDirs.addFirst(parent.getName());
      parent = parent.getOwner();
    }
    return containingDirs.isEmpty() ? null : StringUtil.join(containingDirs, File.separator);
  }
@Override
  public @Nullable String getGroupName(final @NotNull RefElement entity)