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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 compression_type(self):
 """Return the latest compresion type used in this MAR. Returns: One of None, 'bz2', or 'xz' """

        best_compression = None
        for e in self.mardata.index.entries:
            self.fileobj.seek(e.offset)
            magic = self.fileobj.read(10)
            compression = guess_compression(magic)
            if compression == 'xz':
                best_compression = 'xz'
                break
            elif compression == 'bz2' and best_compression is None:
                best_compression = 'bz2'
        return best_compression