public List<Object> getGroupChildrenData(final String groupName) {
    synchronized (myLock) {
      final List<NavigatableMessageElement> children = myGroupNameToMessagesMap.get(groupName);
      if (children == null || children.isEmpty()) {
        return Collections.emptyList();
      }
      final List<Object> result = new ArrayList<>();
      for (NavigatableMessageElement child : children) {
        final Object data = child.getData();
        if (data != null) {
          result.add(data);
        }
      }
      return result;
    }
  }
public List<Object> getGroupChildrenData(final String groupName)