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