return origin json

def refresh_token(self, refresh_token):
        '''return origin json'''
        url = 'https://api.youku.com/oauth2/token.json'
        data = {'client_id': self.client_id,
                'grant_type': 'refresh_token',
                'refresh_token': refresh_token}
        r = requests.post(url, data=data)
        check_error(r)
        return r.json()