code: public void reset() {
      final int ceilingLgK = Util.toLog2(Util.ceilingPowerOf2(reservoirSize_), "ReservoirItemsSketch");
      final int initialLgSize =
              SamplingUtil.startingSubMultiple(ceilingLgK, rf_.lg(), MIN_LG_ARR_ITEMS);
  
      currItemsAlloc_ = SamplingUtil.getAdjustedSize(reservoirSize_, 1 << initialLgSize);
      data_ = new ArrayList<>(currItemsAlloc_);
      itemsSeen_ = 0;
    }
docs: Resets this sketch to the empty state, but retains the original value of k.