@Override
    public HandlerRegistration addDataSelectionHandler(final DataSelectionHandler<TypeFilterPresenter> handler) {
        return getEventBus().addHandlerToSource(DataSelectionEvent.getType(), this, handler);
    }
@return A set of types to include, or empty if the type filter is not active
stroom-core-client/src/main/java/stroom/explorer/client/presenter/TypeFilterPresenter.java