code: function Yubikey(clientId, secretKey) {
    this.clientId = clientId || process.env['YUBIKEY_CLIENT_ID'];
    this.secretKey = secretKey || process.env['YUBIKEY_SECRET_KEY'];
  
    if (!(this.clientId && this.secretKey)) {
      throw new Error("need client id and secret key");
    }
  }
docs: /*
  The Yubikey api has a single method, verify(otp)