docs: def create_comment(self, access_token, video_id, content,
                         reply_id=None, captcha_key=None, captcha_text=None):
          """doc: http://open.youku.com/docs/doc?id=41
          """
          url = 'https://openapi.youku.com/v2/comments/create.json'
          data = {
              'client_id': self.client_id,
              'access_token': access_token,
              'video_id': video_id,
              'content': content,
              'reply_id': reply_id,
              'captcha_key': captcha_key,
              'captcha_text': captcha_text
          }
          data = remove_none_value(data)
          r = requests.post(url, data=data)
          check_error(r)
          return r.json()['id']