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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 set(self, key, value, expires=None, future=None):
 """Set a value """

        # assert the values above
        with self._lock:
            try:
                self._dict[key].set(value, expires=expires, future=future)
            except KeyError:
                self._dict[key] = moment(value, expires=expires, future=future, lock=self._lock)
            return value