doc: http://open.youku.com/docs/doc?id=73

def update_playlist(self, access_token, playlist_id, title,
                        tags=None, category=None, description=None):
        """doc: http://open.youku.com/docs/doc?id=73
        """
        url = 'https://openapi.youku.com/v2/playlists/update.json'
        data = {
            'client_id': self.client_id,
            'access_token': access_token,
            'playlist_id': playlist_id,
            'title': title,
            'tags': tags,
            'category': category,
            'description': description
        }
        data = remove_none_value(data)
        r = requests.post(url, data=data)
        check_error(r)
        return r.json()['id']