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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 timestamp(self):
 """ Compute the normalized canonical timestamp of the mail. """

        # XXX ctime does not refer to creation time on POSIX systems, but
        # rather the last time the inode data changed. Source:
        # https://userprimary.net/posts/2007/11/18
        # /ctime-in-unix-means-last-change-time-not-create-time/
        if self.conf.time_source == CTIME:
            return os.path.getctime(self.path)

        # Fetch from the date header.
        return email.utils.mktime_tz(email.utils.parsedate_tz(
            self.message.get('Date')))