import unittestfrom selenium import webdriverfrom selenium.webdriver.support import expected_conditionsfrom selenium.webdriver.support.wait import WebDriverWaitclass NavigationTest(unittest.TestCase):    def setUp(self):        options = webdriver.FirefoxOptions()        options.add_argument('user-agent="Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) '                             'Chrome/69.0.3497.100 Safari/537.36"')        self.driver = webdriver.Firefox()        self.driver.implicitly_wait(30)        self.driver.maximize_window()        # navigate to the application home page        self.driver.get("http://duckduckgo.com/")    def tearDown(self):        self.driver.quit()    def test_browser_navigation(self):        driver = self.driver        # get the search textbox        search_field = self.driver.find_element_by_name("q")        search_field.clear()        # enter search keyword and submit        search_field.send_keys("selenium")        search_field.submit()        se_wd_link = driver.find_element_by_link_text("Selenium")        se_wd_link.click()        self.assertEqual("SeleniumHQ Browser Automation", driver.title)        driver.back()        self.assertTrue(            WebDriverWait(self.driver, 10).until(                expected_conditions.title_is("selenium at DuckDuckGo")            )        )        driver.forward()        self.assertTrue(            WebDriverWait(self.driver, 10).until(                expected_conditions.title_is("SeleniumHQ Browser Automation")            )        )        driver.refresh()        self.assertTrue(            WebDriverWait(self.driver, 10).until(                expected_conditions.title_is("SeleniumHQ Browser Automation")            )        )if __name__ == "__main__":    unittest.main()