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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 epoch(self):
 """GPS epoch associated with these data :type: `~astropy.time.Time` """

        try:
            if self._epoch is None:
                return None
            return Time(*modf(self._epoch)[::-1], format='gps', scale='utc')
        except AttributeError:
            self._epoch = None
            return self._epoch