code: public void releaseEvent(EventId eventId) throws Exception {
  		Lockable<V> eventWrapper = sharedBuffer.getEvent(eventId);
  		if (eventWrapper != null) {
  			if (eventWrapper.release()) {
  				sharedBuffer.removeEvent(eventId);
  			} else {
  				sharedBuffer.upsertEvent(eventId, eventWrapper);
  			}
  		}
  	}
docs: Decreases the reference counter for the given event so that it can be
  removed once the reference counter reaches 0.
  
  @param eventId id of the event
  @throws Exception Thrown if the system cannot access the state.