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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 fasta(args):
 """ %prog fasta bedfile scf.fasta pseudomolecules.fasta Use OM bed to scaffold and create pseudomolecules. bedfile can be generated by running jcvi.assembly.opticalmap bed --blockonly """

    from jcvi.formats.sizes import Sizes
    from jcvi.formats.agp import OO, build

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

    if len(args) != 3:
        sys.exit(not p.print_help())

    bedfile, scffasta, pmolfasta = args
    pf = bedfile.rsplit(".", 1)[0]
    bed = Bed(bedfile)
    selected = select_bed(bed)
    oo = OO()
    seen = set()
    sizes = Sizes(scffasta).mapping
    agpfile = pf + ".agp"
    agp = open(agpfile, "w")
    for b in selected:
        scf = range_parse(b.accn).seqid
        chr = b.seqid
        cs = (chr, scf)
        if cs not in seen:
            oo.add(chr, scf, sizes[scf], b.strand)
            seen.add(cs)
        else:
            logging.debug("Seen {0}, ignored.".format(cs))

    oo.write_AGP(agp, gaptype="contig")
    agp.close()
    build([agpfile, scffasta, pmolfasta])