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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 clear(self):
 """Clears the cache."""

        if self._cache is None:
            return _NO_RESULTS
        if self._cache is not None:
            with self._cache as k:
                res = [x.as_operation() for x in k.values()]
                k.clear()
                k.out_deque.clear()
                return res