code: function normalizeUnits(units, momentObj) {
      if (isJalali(momentObj)) {
          units = toJalaliUnit(units);
      }
      if (units) {
          var lowered = units.toLowerCase();
          units = unitAliases[lowered] || lowered;
      }
      // TODO : add unit test
      if (units === "jday") units = "day";
      else if (units === "jd") units = "d";
      return units;
  }
docs: normalize units to be comparable
  @param {string} units