docs: static DoublesUnionImplR wrapInstance(final Memory mem) {
      final DirectUpdateDoublesSketchR sketch = DirectUpdateDoublesSketchR.wrapInstance(mem);
      final int k = sketch.getK();
      final DoublesUnionImplR union = new DoublesUnionImplR(k);
      union.maxK_ = k;
      union.gadget_ = sketch;
      return union;
    }