code: function() {
        var cert = this.keychain.getCertPem();
        if (!cert) {
          throw new CError('missing certificate').log();
        }
        var tmp = this.getDate() + '::' + cert + '::' + SECRET_CLIENT;
        var hmac = forge.hmac.create();
        hmac.start('sha256', SECRET);
        hmac.update(tmp);
        return hmac.digest().toHex();
      }
docs: Generate a valid token
  
  @returns {String} The token