code: public String extractTransition(XEvent event) {
  		XAttribute attribute = event.getAttributes().get(KEY_TRANSITION);
  		if (attribute == null) {
  			return null;
  		} else {
  			return ((XAttributeLiteral) attribute).getValue();
  		}
  	}
docs: Extracts the lifecycle transition string from a given event.
  
  @param event
  An event.
  @return The lifecycle transition string of this event. Can be
  <code>null</code>, if not defined.