anchor.diff:  
     static Future<EJDB2> _open(EJDB2Builder b) async {
       final hdl =
  -        await _mc.invokeMethod<int>('open', [null, b.path, b._asOpts()]).catchError(_handleError);
  +        await _mc.invokeMethod<int>('open', [null, b.path, b._asOpts()]).catchError(_errorHandler<int>());
       return EJDB2._(hdl);
     }
   
  
positive.code:         (json is! String) ? convert_lib.jsonEncode(json) : json as String,
          id
        ])
        .catchError(_handleError)
        .then((v) => v as int));
  
    /// Apply rfc6902/rfc6901 JSON [patch] to the document identified by [id].
  
negative.code:       };
  }
  
  FutureOr<T> Function(Object, StackTrace) _errorHandler<T>() =>
    (Object err, StackTrace s) {
      if (err is PlatformException && err.code.startsWith('@ejdb')) {
      return Future<T>.error(EJDB2Error(err.code, err.message), s);
      }
      return Future<T>.error(err, s);
    };
  
  class EJDB2Error implements Exception {
    EJDB2Error(this.code, this.message);
  