Add a new JSON object to an existing list array firebase firestore

My app has a feature where users can add their reviews. For example, it's like leaving a comment on Facebook. posting a user review should be stored in the reviews list. I think it can't be done this way .doc(DocId).update(review.toJson()).

This is a screenshot of the data structure of my firebase firestore.

I tried to solve this firestore.FieldValue if I do that, an error massage will come like this: I/flutter (21250): type '_Map<String, String?>' is not a subtype of type 'List<dynamic>'

this is my firestore query.

Future<void> addReview (placeId,Review review) async{    try{      await FirebaseFirestore.instance.collection('attractions')      .where('placeId',isEqualTo: placeId).get()      .then((querySnapshot) {        for (var ele in querySnapshot.docs) {            FirebaseFirestore.instance            .collection('attractions')            .doc(ele.id)            .update({'reviews': FieldValue.arrayUnion(review.toJson())});        }      });    }catch(e){      print(e);    }  }}

this is my review.dart model class :

class Review {  final String reviewId;  final String? name;  final String publishAt;  final String? reviewerPhotoUrl;  final String text;  Review({    required this.reviewId,    required this.name,    required this.publishAt,    required this.reviewerPhotoUrl,    required this.text,  });  toJson ()=>{"reviewId":reviewId,"name":name,"publishAt":publishAt,"reviewerPhotoUrl":reviewerPhotoUrl,"text":text  };}

I think there is a way around this or there is an alternative to doing this.