code: function _headers(accessToken, options, data) {
    var headers = (options && options.headers) || {};
    headers['Content-Type'] = 'application/json';
    if (data) {
      try {
        headers['Content-Length'] = Buffer.byteLength(data, 'utf8');
      } catch (e) {
        logger.error('Could not get the content length of the data');
      }
    }
    headers['X-Rollbar-Access-Token'] = accessToken;
    return headers;
  }
docs: Helpers *