private @NotNull Pair<ActionCallback, List<ActionCallback>> getReadyCallbacks(Object readyRequestor) {
      synchronized (myReadyCallbacks) {
        ActionCallback done = myReadyCallbacks.get(readyRequestor);
        if (done == null) {
          done = new ActionCallback();
        }

        myReadyCallbacks.remove(readyRequestor);
        ArrayList<ActionCallback> rejected = new ArrayList<>(myReadyCallbacks.values());
        myReadyCallbacks.clear();
        return new Pair<>(done, rejected);
      }
    }
private @NotNull Pair<ActionCallback, List<ActionCallback>> getReadyCallbacks(Object readyRequestor)