code: public static long[] toBitset(Itemset i, long[] bits) {
      for(int it = i.iter(); i.iterValid(it); it = i.iterAdvance(it)) {
        BitsUtil.setI(bits, i.iterDim(it));
      }
      return bits;
    }
docs: Get the items.
  
  @param i Itemset
  @param bits Output bitset (must be zeros)
  @return Output bitset