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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 _compress(self):
 """Internal method to compress the cache. This method will expire any old items in the cache, making the cache smaller"""


        # Don't compress too often
        now = time.time()
        if self._last_compression + self._compression_timer < now:
            self._last_compression = now
            for key in list(self._store.keys()):
                self.get(key)