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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 log(args):
 """ %prog log logfile Prepare a log of created files, ordered by their creation data. The purpose for this script is to touch these files sequentially to reflect their build order. On the JCVI scratch area, the files are touched regularly to avoid getting deleted, losing their respective timestamps. However, this created a problem for the make system adopted by ALLPATHS. An example block to be extracted ==> [PC] Calling PreCorrect to create 2 file(s):
 [PC] [PC] $(RUN)/frag_reads_prec.fastb [PC] $(RUN)/frag_reads_prec.qualb [PC] [PC] from 2 file(s):
 [PC] [PC] $(RUN)/frag_reads_filt.fastb [PC] $(RUN)/frag_reads_filt.qualb """

    from jcvi.algorithms.graph import nx, topological_sort

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

    if len(args) != 1:
        sys.exit(not p.print_help())

    g = nx.DiGraph()

    logfile, = args
    fp = open(logfile)
    row = fp.readline()
    incalling = False
    basedb = {}

    while row:
        atoms = row.split()
        if len(atoms) < 3:
            row = fp.readline()
            continue

        tag, token, trailing = atoms[0], atoms[1], atoms[-1]
        if trailing == 'file(s):':
            numfiles = int(atoms[-2])
            row = fp.readline()
            assert row.strip() == tag

            if token == "Calling" and not incalling:
                createfiles = []
                for i in xrange(numfiles):
                    row = fp.readline()
                    createfiles.append(row.split()[-1])
                incalling = True

            if token == "from" and incalling:
                fromfiles = []
                for i in xrange(numfiles):
                    row = fp.readline()
                    fromfiles.append(row.split()[-1])

                for a in fromfiles:
                    for b in createfiles:
                        ba, bb = op.basename(a), op.basename(b)
                        basedb[ba] = a
                        basedb[bb] = b
                        g.add_edge(ba, bb)

                incalling = False

        if token == "ln":
            fromfile, createfile = atoms[-2:]
            ba, bb = op.basename(fromfile), op.basename(createfile)
            #print ba, "-->", bb
            if ba != bb:
                g.add_edge(ba, bb)

        row = fp.readline()

    ts = [basedb[x] for x in topological_sort(g) if x in basedb]
    print("\n".join(ts))