def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def init(num_players):
	global MAP_WIDTH,MAP_HEIGHT,N_ITERATIONS,H_RATIO,W_RATIO,MIN_ROOM_SIDE,CENTER_HUB_HOLE,CENTER_HUB_RADIO,MAP_NAME
	MAP_WIDTH=int(500*sqrt(num_players))
	MAP_HEIGHT=MAP_WIDTH
	N_ITERATIONS=log(MAP_WIDTH*100,2)
	H_RATIO=0.49
	W_RATIO=H_RATIO
	MIN_ROOM_SIDE = 32
	CENTER_HUB_HOLE = 32
	CENTER_HUB_RADIO = CENTER_HUB_HOLE-MIN_ROOM_SIDE/2
	MAP_NAME="result%s.png"%MAP_WIDTH