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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 nucmer(args):
 """ %prog nucmer ref.fasta query.fasta Run NUCMER using query against reference. Parallel implementation derived from: <https://github.com/fritzsedlazeck/sge_mummer> """

    from itertools import product

    from jcvi.apps.grid import MakeManager
    from jcvi.formats.base import split

    p = OptionParser(nucmer.__doc__)
    p.add_option("--chunks", type="int",
                 help="Split both query and subject into chunks")
    p.set_params(prog="nucmer", params="-l 100 -c 500")
    p.set_cpus()
    opts, args = p.parse_args(args)

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

    ref, query = args
    cpus = opts.cpus
    nrefs = nqueries = opts.chunks or int(cpus ** .5)
    refdir = ref.split(".")[0] + "-outdir"
    querydir = query.split(".")[0] + "-outdir"
    reflist = split([ref, refdir, str(nrefs)]).names
    querylist = split([query, querydir, str(nqueries)]).names

    mm = MakeManager()
    for i, (r, q) in enumerate(product(reflist, querylist)):
        pf = "{0:04d}".format(i)
        cmd = "nucmer -maxmatch"
        cmd += " {0}".format(opts.extra)
        cmd += " {0} {1} -p {2}".format(r, q, pf)
        deltafile = pf + ".delta"
        mm.add((r, q), deltafile, cmd)
        print(cmd)

    mm.write()