def find_playlist_by_id(self, playlist_id):
        """doc: http://open.youku.com/docs/doc?id=66
        """
        url = 'https://openapi.youku.com/v2/playlists/show.json'
        params = {
            'client_id': self.client_id,
            'playlist_id': playlist_id
        }
        r = requests.get(url, params=params)
        check_error(r)
        return r.json()