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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 bed_to_bedpe(bedfile, bedpefile, pairsbedfile=None, matesfile=None, ca=False, strand=False):
 """ This converts the bedfile to bedpefile, assuming the reads are from CA. """

    fp = must_open(bedfile)
    fw = must_open(bedpefile, "w")
    if pairsbedfile:
        fwpairs = must_open(pairsbedfile, "w")

    clones = defaultdict(list)
    for row in fp:
        b = BedLine(row)
        name = b.accn
        clonename = clone_name(name, ca=ca)
        clones[clonename].append(b)

    if matesfile:
        fp = open(matesfile)
        libraryline = next(fp)
        # 'library bes     37896   126916'
        lib, name, smin, smax = libraryline.split()
        assert lib == "library"
        smin, smax = int(smin), int(smax)
        logging.debug("Happy mates for lib {0} fall between {1} - {2}".\
                      format(name, smin, smax))

    nbedpe = 0
    nspan = 0
    for clonename, blines in clones.items():
        nlines = len(blines)
        if nlines == 2:
            a, b = blines
            aseqid, astart, aend = a.seqid, a.start, a.end
            bseqid, bstart, bend = b.seqid, b.start, b.end
            outcols = [aseqid, astart - 1, aend, bseqid, bstart - 1, bend, clonename]
            if strand:
                outcols.extend([0, a.strand, b.strand])
            print("\t".join(str(x) for x in outcols), file=fw)
            nbedpe += 1
        elif nlines == 1:
            a, = blines
            aseqid, astart, aend = a.seqid, a.start, a.end
            bseqid, bstart, bend = 0, 0, 0
        else:  # More than two lines per pair
            pass

        if pairsbedfile:
            start = min(astart, bstart) if bstart > 0 else astart
            end = max(aend, bend) if bend > 0 else aend
            if aseqid != bseqid:
                continue

            span = end - start + 1
            if (not matesfile) or (smin <= span <= smax):
                print("\t".join(str(x) for x in \
                        (aseqid, start - 1, end, clonename)), file=fwpairs)
                nspan += 1

    fw.close()
    logging.debug("A total of {0} bedpe written to `{1}`.".\
                  format(nbedpe, bedpefile))
    if pairsbedfile:
        fwpairs.close()
        logging.debug("A total of {0} spans written to `{1}`.".\
                      format(nspan, pairsbedfile))