docs: public static Vec compose(TransfVec origVec, int[][] transfMap, String[] domain, boolean keepOrig) {
      // Do a mapping from INT -> ENUM -> this vector ENUM
      int[][] domMap = Utils.compose(new int[][] {origVec._values, origVec._indexes }, transfMap);
      Vec result = origVec.masterVec().makeTransf(domMap[0], domMap[1], domain);;
      if (!keepOrig) DKV.remove(origVec._key);
      return result;
    }