code: protected Boolean handleRememberMeCookie(String[] valueAry, RememberMeLoginSpecifiedOption option) {
          if (valueAry.length != 2) { // invalid cookie
              return null;
          }
          final String userKey = valueAry[0]; // resolved by identity login
          final String expireDate = valueAry[1]; // AccessToken's expire
          if (isValidRememberMeCookie(userKey, expireDate)) {
              final ID userId = convertCookieUserKeyToUserId(userKey);
              return doRememberMe(userId, expireDate, option);
          }
          return null;
      }
docs: Handle remember-me cookie (and do remember-me). <br>
  You can change access token's structure by override. #change_access_token
  @param valueAry The array of cookie values. (NotNull)
  @param option The option of remember-me login specified by caller. (NotNull)
  @return The determination of remember-me, true or false or null. (NullAllowed: means invalid cookie)