toMap method Null safety

Implementation

@override
Map<String, Object?> toMap() {
  return {
    'name': this.name,
    'pt': this.pt?.toMap(),
    'address': this.address,
    'phone': this.phone,
    'uid': this.uid,
    'province': this.province,
    'city': this.city,
    'area': this.area,
    'streetID': this.streetID,
    'tag': this.tag,
    'hasDetailInfo': this.hasDetailInfo,
    'detailInfo': this.detailInfo?.toMap(),
    'direction': this.direction,
    'distance': this.distance,
    'zipCode': this.zipCode,
    'parentPOI': this.parentPOI?.toMap(),
    'adcode': this.adcode,
  };
}