code: function (options, cb, wd, params) {
        // if no cb is given, generate a body with the `desiredCapabilities` object
        if (!cb) {
          // check if we have parameters set up
          if (Object.keys(params).length > 0) {
            return JSON.stringify(params);
          }
          return '';
        }
  
        // invoke the given callback & stringify
        var data = cb.call(wd, params);
        return data === null ? '{}' : JSON.stringify(data);
      }
docs: Generates the message body for webdriver client requests of type POST
  
  @method generateBody
  @param {object} options Browser options (name, bin path, etc.)
  @param {function|undefined} cb Callback function that should be invoked to generate the message body
  @param {Dalek.Internal.Webdriver} wd Webdriver base object
  @param {object} params Parameters that should be part of the message body
  @return {string} body Serialized JSON of body request data