@Override
  public @NotNull ActionCallback getReady(@NotNull Object requestor) {
    Content selected = getSelectedContent();
    if (selected == null) return ActionCallback.DONE;
    BusyObject busyObject = selected.getBusyObject();
    return busyObject != null ? busyObject.getReady(requestor) : ActionCallback.DONE;
  }
@Override
  public @NotNull ActionCallback getReady(@NotNull Object requestor)