code: public void select(TimelineEvent event, TimelineUpdater timelineUpdater) {
          int index = getIndex(event);
  
          if (timelineUpdater != null) {
              // update UI
              timelineUpdater.select(index);
          }
      }
docs: Selects a given event in UI visually. To unselect all events, pass a null as event.
  
  @param event           event to be selected
  @param timelineUpdater TimelineUpdater instance to select the event in UI