docs: public void update(final Memory mem, final ArrayOfItemsSerDe<T> serDe) {
      if (mem == null) {
        return;
      }
  
      ReservoirItemsSketch<T> ris = ReservoirItemsSketch.heapify(mem, serDe);
      ris = (ris.getK() <= maxK_ ? ris : ris.downsampledCopy(maxK_));
  
      if (gadget_ == null) {
        createNewGadget(ris, true);
      } else {
        twoWayMergeInternal(ris, true);
      }
    }