http://api.yandex.ru/cleanweb/doc/dg/concepts/get-captcha.xml

def get_captcha(self, id=None):
        """ http://api.yandex.ru/cleanweb/doc/dg/concepts/get-captcha.xml"""
        payload = {'id': id}
        r = self.request('get', 'http://cleanweb-api.yandex.ru/1.0/get-captcha', params=payload)
        return dict((item.tag, item.text) for item in ET.fromstring(r.content))