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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 blast(self, blastfile=None, outfile=None):
 """ convert anchor file to 12 col blast file """

        from jcvi.formats.blast import BlastSlow, BlastLineByConversion

        if not outfile:
            outfile = self.filename + ".blast"

        if blastfile is not None:
            blasts = BlastSlow(blastfile).to_dict()
        else:
            blasts = None

        fw = must_open(outfile, "w", checkexists=True)
        nlines = 0
        for a, b, id in self.iter_pairs():
            if (a, b) in blasts:
                bline = blasts[(a, b)]
            elif (b, a) in blasts:
                bline = blasts[(b, a)]
            else:
                line = "\t".join((a, b))
                bline = BlastLineByConversion(line, mode="110000000000")

            print(bline, file=fw)
            nlines += 1
        fw.close()

        logging.debug("A total of {0} BLAST lines written to `{1}`."\
                        .format(nlines, outfile))

        return outfile