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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 blat(args):
 """ %prog blat map1.txt ref.fasta Make ALLMAPS input csv based on sequences. The tab-delimited txt file include: name, LG, position, sequence. """

    from jcvi.formats.base import is_number
    from jcvi.formats.blast import best as blast_best, bed as blast_bed
    from jcvi.apps.align import blat as blat_align

    p = OptionParser(blat.__doc__)
    opts, args = p.parse_args(args)

    if len(args) != 2:
        sys.exit(not p.print_help())

    maptxt, ref = args
    pf = maptxt.rsplit(".", 1)[0]
    register = {}
    fastafile = pf + ".fasta"
    fp = open(maptxt)
    fw = open(fastafile, "w")
    for row in fp:
        name, lg, pos, seq = row.split()
        if not is_number(pos):
            continue
        register[name] = (pf + '-' + lg, pos)
        print(">{0}\n{1}\n".format(name, seq), file=fw)
    fw.close()

    blatfile = blat_align([ref, fastafile])
    bestfile = blast_best([blatfile])
    bedfile = blast_bed([bestfile])
    b = Bed(bedfile).order

    pf = ".".join((op.basename(maptxt).split(".")[0],
                   op.basename(ref).split(".")[0]))
    csvfile = pf + ".csv"
    fp = open(maptxt)
    fw = open(csvfile, "w")
    for row in fp:
        name, lg, pos, seq = row.split()
        if name not in b:
            continue
        bbi, bb = b[name]
        scaffold, scaffold_pos = bb.seqid, bb.start
        print(",".join(str(x) for x in \
                    (scaffold, scaffold_pos, lg, pos)), file=fw)
    fw.close()