隐式的wait()缺少1个必需的位置参数

我正在用Python学习Selenium,在一个教程中我发现了以下代码。

from selenium import webdriver
from time import gmtime, strftime
import unittest
#from builtins import classmethod

class RegisterNewUser(unittest.TestCase):
    #@classmethod
    def setUp(self):
        self.driver = webdriver.Firefox
        self.driver.implicitly_wait(30)
        self.driver.maximize_window()

        # navigate to the application home page
        self.driver.get("http://demo-store.seleniumacademy.com/")

    def test_register_new_user(self):
        driver = self.driver
        pass

    def tearDown(self):
        self.driver.quit()

if __name__ == "__main__":
    unittest.main(verbosity=2)

它抛出一个错误:

File "register_new_user.py", line 10, in setUp
    self.driver.implicitly_wait(30)
TypeError: implicitly_wait() missing 1 required positional argument: 'time_to_wait'

我试图添加注释掉的代码( classmethod )但不会改变任何事。没有 test_register_new_user 不会出错。

我使用的是Python 3.6.4、Selenium 3.141(和GeckoDriver 0.23)