请求帮助

from selenium import webdriver

driver = webdriver.Chrome()
driver.get('http://47.100.225.199/index.php?s=/index/user/logininfo.html')
driver.implicitly_wait(5)


#定位登录账号
driver.find_element_by_css_selector('[name="accounts"]').send_keys('helloworld')
#定位密码输入框
driver.find_element_by_css_selector('[name="pwd"]').send_keys('123456')

#定位验证码图片
verify_image = driver.find_element_by_css_selector('[id="form-verify-img"]')
verify_image.screenshot('./verifyphoto.png')  //这段代码会报错



错误提示：selenium.common.exceptions.WebDriverException: Message: unknown command: session/01f6d3f933016464d22f013fa15d0618/element/0.5098749452052003-3/screenshot
求教问题出在哪里，谢谢