How to use the loopback4-authentication.AuthErrorKeys.TokenExpired function in loopback4-authentication

async exchangeToken(
    @requestBody() req: AuthRefreshTokenRequest,
  ): Promise {
    const refreshPayload: RefreshToken = await this.refreshTokenRepo.get(
      req.refreshToken,
    );
    if (!refreshPayload) {
      throw new HttpErrors.Unauthorized(AuthErrorKeys.TokenExpired);
    }
    const authClient = await this.authClientRepository.findOne({
      where: {
        clientId: refreshPayload.clientId,
      },
    });
    if (!authClient) {
      throw new HttpErrors.Unauthorized(AuthErrorKeys.ClientInvalid);
    }
    return this.createJWT(
      {clientId: refreshPayload.clientId, userId: refreshPayload.userId},
      authClient,
    );
  }