public delegate PersistentFSMBaseTState, TData, TEventState StateFunction(
	FSMBaseEvent<TData> fsmEvent,
	PersistentFSMBaseTState, TData, TEventState state = null
)

type StateFunction = 
    delegate of 
        fsmEvent : FSMBaseEvent<'TData> * 
        ?state : PersistentFSMBaseTState, TData, TEventState 
(* Defaults:
        let _state = defaultArg state null
*)
-> PersistentFSMBaseTState, TData, TEventState