anchor.diff:  
     World(this.id, this.randomnumber);
   
  -  toJson() => { "id": id, "randomnumber": randomnumber };
  +  toJson() => { "id": id, "randomNumber": randomnumber };
   }
   
   main() {
  
positive.code:     .then((worlds) {
        var result = worlds.map((world) {
          return {
            "id": world["id"],
            "randomnumber": world["randomnumber"]
          };
        });
        connect.response.write(json.stringify(result.toList()));
  
negative.code: // runs a mongo query and returns a promise
  _mongoQuery() {
    return _worldCollection.findOne({
      "_id": _RANDOM.nextInt(_WORLD_TABLE_SIZE) + 1
    });
  }
  