code: public String takeScreenShot(Driver driver, String fileName) {
      return ifWebDriverStarted(driver, webDriver ->
        ifReportsFolderNotNull(driver.config(), config ->
          takeScreenShot(config, webDriver, fileName)));
    }
docs: Takes screenshot of current browser window.
  Stores 2 files: html of page (if "savePageSource" option is enabled), and (if possible) image in PNG format.
  
  @param fileName name of file (without extension) to store screenshot to.
  @return the name of last saved screenshot or null if failed to create screenshot