code: public void switchToParentWindow() {
          String action = "Switching back to parent window";
          String expected = "Parent window is available and selected";
          try {
              driver.switchTo().window(parentWindow);
          } catch (Exception e) {
              reporter.fail(action, expected, "Parent window was unable to be selected. " + e.getMessage());
              log.warn(e);
              return;
          }
          reporter.pass(action, expected, expected);
      }
docs: Switches to the originally opened window. This is an alternative to
  switchNextTab or switchPreviousTab, as this works better for some systems
  and environments that others.