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kotlinlang

I have a Google Map, and depending of a `mapState.mapPois` list, I'm displaying the markers of the map:
```@Composable fun MapPanel(mapState: MapState, [...]) {
    GoogleMap() {
        for (busStop in mapState.busStops) { Marker([...]) }```
The parametrized mapstate is collected like this on the parent composable: `val mapState by vm.mapState.collectAsStateWithLifecycle()`
And is being stored as a state like this on the vm:
```data class MapState(val busStops: List<BusStop> = emptyList(),}
[...]
protected val _mapState = MutableStateFlow(MapState())
val mapState: StateFlow<MapState> = _mapState```
When `mapState.busStop` list is modified on the vm, the map is not being recomposed:
```_mapState.update { currentState -> currentState.copy(busStops = favoriteBusStopsList) }```
The only way I got the recomposition being triggered is embedding the for that iterates mapState.busStops into a `key(mapState.busStops) {` like this:
```@Composable fun MapPanel(mapState: MapState, [...]) {
    GoogleMap() {
        key(mapState.busStops) { for (busStop in mapState.busStops) { Marker([...]) } }```
*can someone explain me why it's necessary to embed it into key and why recomposition does not trigger if not? Thank you*