anchor.diff:  
   /** BsonBinary BSON Type **/
   const _BSON_DATA_BINARY = 5;
  +
  +/** undefined BSON Type **/
  +const _BSON_DATA_UNDEFINED = 6;
   
   /** ObjectID BSON Type **/
   const _BSON_DATA_OID = 7;
  
positive.code: const _BSON_DATA_CODE = 13;
  
  /** Timestamp BSON Type **/
  const _BSON_DATA_TIMESTAMP = 17; 
  
  /** The following types are implemented partially **/
  //static const BSON_DATA_MIN_KEY = 0xff; MinKey BSON Type
  
negative.code:       return new BsonArray([]);
      case _BSON_DATA_OBJECT:
        return new BsonMap({});
      case _BSON_DATA_UNDEFINED:
        return new BsonNull();
      case _BSON_DATA_OID:
        return new ObjectId();
      case _BSON_DATA_NULL:
  