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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def expireat(self, key, timestamp):
 """Set expire timestamp on a key. if timeout is float it will be multiplied by 1000 coerced to int and passed to `pexpireat` method. Otherwise raises TypeError if timestamp argument is not int. """

        if isinstance(timestamp, float):
            return self.pexpireat(key, int(timestamp * 1000))
        if not isinstance(timestamp, int):
            raise TypeError("timestamp argument must be int, not {!r}"
                            .format(timestamp))
        fut = self.execute(b'EXPIREAT', key, timestamp)
        return wait_convert(fut, bool)