def expire_leaderboard_at(self, timestamp):
self.expire_leaderboard_at_for(self.leaderboard_name, timestamp)<EOL>
Expire the current leaderboard at a specific UNIX timestamp. Do not use this with
leaderboards that utilize member data as there is no facility to cascade the
expiration out to the keys for the member data.

@param timestamp [int] UNIX timestamp at which the leaderboard will be expired.