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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 _cleanup(self):
 """Cleanup the stored sessions"""

        current_time = time.time()
        timeout = self._config.timeout
        if current_time - self._last_cleanup_time > timeout:
            self.store.cleanup(timeout)
            self._last_cleanup_time = current_time