<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def cleanup(self):
 """Delete expired nonces"""

        t = time.time()
        for noncefile in glob(self.path + '/*.nonce'):
            if os.path.getmtime(noncefile) + self.expiration > t:
                os.unlink(noncefile)