private static void DefineMachine(IAsyncStateMachine <State, Event> fsm)
{
fsm.In(State.A)
.On(Event.S2).Goto(State.S2)
.On(Event.X);
fsm.In(State.B)
.On(Event.S).Goto(State.S)
.On(Event.X);
fsm.DefineHierarchyOn(State.S)
.WithHistoryType(HistoryType.Deep)
.WithInitialSubState(State.S1)
.WithSubState(State.S2);
fsm.In(State.S)
.On(Event.B).Goto(State.B);
}