cancel
Gets a flag indicating whether the event is to be canceled or not. True implies that the event is to be canceled. It is up to the executive to handle the cancellation. If the event is canceled, it's execute method will not be called when it becomes the current event. Thus, an event can be canceled or uncanceled at any simulated time prior to when the event is scheduled to occur. It is an error to attempt to cancel an event that is not scheduled.