Lifecycle methods
This is the collection of lifecycle methods within the Checkpoints interface. There are only three lifecycle methods, clear, clearForward, and destroy.
clear
The clear method resets this Checkpoints object to its initial state, removing all the checkpoints it has been managing.
clearForward
The clearForward method resets just the 'redo' checkpoints it has been managing.
destroy
The destroy method should be called when this Checkpoints object is no longer used.