<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def close(self):
 """ Close this file and commit it to its permanent location. @return: a Deferred which fires when the file has been moved (and backed up to tertiary storage, if necessary). """

        now = time.time()
        try:
            file.close(self)
            _mkdirIfNotExists(self._destpath.dirname())
            self.finalpath = self._destpath
            os.rename(self.name, self.finalpath.path)
            os.utime(self.finalpath.path, (now, now))
        except:
            return defer.fail()
        return defer.succeed(self.finalpath)