code: function() {
        if (this.getMode() !== mode) {
          throw new CError('unexpected mode').log();
        }
        var cert;
        try {
          cert = this.keychain.getCertPem();
        } catch (e) {
          throw new CError({
            body: {
              code: 'ImATeapot',
              message: 'missing certificate',
              cause: e
            }
          }).log('body');
        }
        if (!cert) {
          throw new CError('missing certificate').log();
        }
        var out = {
          mode: this.getMode(),
          cert: cert
        };
        if (this.getSid()) {
          out.sid = this.getSid();
        }
        return out;
      }
docs: Get the payload property of the header
  
  @return {Object} The payload property of the header