onSeatListChanged property
5.2 Seat List Changed Event
seatList The current latest user list on the seat, including newly seated users.
seatedList The list of newly seated users.
leftList The list of users who have recently left their seats.
Implementation
OnSeatListChanged onSeatListChanged = (List<TUISeatInfo> seatList,
    List<TUISeatInfo> seatedList, List<TUISeatInfo> leftList) {};