code: def Focus(cls):
          
          
          element = cls._element()        
  #         element.send_keys(Keys.NULL)        
          action = ActionChains(Web.driver)
          action.send_keys_to_element(element, Keys.NULL)
          action.perform()
docs: 在指定输入框发送 Null， 用于设置焦点
          @note: key event ->  NULL