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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 save_trailer(self, tocpos):
 """Save the trailer to disk. CArchives can be opened from the end - the trailer points back to the start. """

        totallen = tocpos + self.toclen + self.TRLLEN
        pyvers = sys.version_info[0]*10 + sys.version_info[1]
        trl = struct.pack(self.TRLSTRUCT, self.MAGIC, totallen,
                          tocpos, self.toclen, pyvers)
        self.lib.write(trl)