code: public JSON with(MapBuilder b) {
          JSONReader r = _reader.with(b);
          if (r == _reader) {
              return this;
          }
          return _with(_features, _streamFactory, _treeCodec,
                  r, _writer, _prettyPrinter);
      }
docs: Mutant factory for constructing an instance with specified {@link MapBuilder},
  and returning new instance (or, if there would be no change, this instance).