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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 modified(self):
        '''
        Get human-readable last modification date-time.

        :returns: iso9008-like date-time string (without timezone)
        :rtype: str
        '''
        try:
            dt = datetime.datetime.fromtimestamp(self.stats.st_mtime)
            return dt.strftime('%Y.%m.%d %H:%M:%S')
        except OSError:
            return None