def test_findkeyboard(self):
    el = self.driver.find_element_by_class_name('UIAKeyboard')
    print(el.is_displayed())

执行以上 test 的时候直接报错
An element could not be located on the page using the given search parameters.

求助下 is_display() 这样的函数应该怎么使用

/usr/bin/python "/Applications/PyCharm CE.app/helpers/pycharm/utrunner.py" /Users/Alfred/sample-code-master/sample-code/examples/python/sapi_login_test.py::SapiHomePageTests::test_findkeyboard true
Testing started at 下午5:57 ...

Error
Traceback (most recent call last):
  File "/Users/Alfred/sample-code-master/sample-code/examples/python/sapi_login_test.py", line 44, in test_findkeyboard
    el = self.driver.find_element_by_class_name('UIAKeyboard')
  File "/Library/Python/2.7/site-packages/selenium-2.41.0-py2.7.egg/selenium/webdriver/remote/webdriver.py", line 343, in find_element_by_class_name
    return self.find_element(by=By.CLASS_NAME, value=name)
  File "/Library/Python/2.7/site-packages/selenium-2.41.0-py2.7.egg/selenium/webdriver/remote/webdriver.py", line 655, in find_element
    {'using': by, 'value': value})['value']
  File "/Library/Python/2.7/site-packages/selenium-2.41.0-py2.7.egg/selenium/webdriver/remote/webdriver.py", line 166, in execute
    self.error_handler.check_response(response)
  File "build/bdist.macosx-10.9-intel/egg/appium/webdriver/errorhandler.py", line 29, in check_response
    raise wde
NoSuchElementException: Message: u'An element could not be located on the page using the given search parameters.'