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

def check_captcha(self, captcha, value, id=None):
        """ http://api.yandex.ru/cleanweb/doc/dg/concepts/check-captcha.xml"""
        payload = {'captcha': captcha,
                   'value': value,
                   'id': id}
        r = self.request('get', 'http://cleanweb-api.yandex.ru/1.0/check-captcha', params=payload)
        root = ET.fromstring(r.content)
        if root.findall('ok'):
            return True
        if root.findall('failed'):
            return False