Callback object for Interaction type events.
This, like all other callback objects are automatically reused and you should not keep any reference to them.
Existing arbiters between interactors.
This list will at present contain 'all' arbiters, not just those matching the interactionType in the InteractionListener. (This may be subject to change).
First Interactor involved in callback event.
This interactor will have CbType set matched by the first OptionType in InteractionListener