def expire_at(time)
      time = (time.to_f * 1000).floor
      return coerce_bool(self.connection.pexpireat(@key, time))
    end
def expire_at(time)
      time = (time.to_f * 1000).floor
      return coerce_bool(self.connection.pexpireat(@key, time))
    end
Sets the key to expire at the given timestamp.
 @param [#to_f] time time or unix timestamp at which the key should expire; once converted to float, assumes 1.0 is one second, 0.001 is 1 ms
 @return [Boolean] true if expired, false otherwise