code: public void addExtraCapabilities(DesiredCapabilities extraCapabilities) {
          if (extraCapabilities != null && browser.getName() != BrowserName.NONE) {
              desiredCapabilities = desiredCapabilities.merge(extraCapabilities);
          }
      }
docs: If additional capabilities are provided in the test case, add them in
  
  @param extraCapabilities any additional parameters to set for selenium