def plot(args):
    """
    %prog plot workdir sample chr1,chr2

    Plot some chromosomes for visual proof. Separate multiple chromosomes with
    comma. Must contain folder workdir/sample-cn/.
    """
    from jcvi.graphics.base import savefig

    p = OptionParser(plot.__doc__)
    opts, args, iopts = p.set_image_options(args, figsize="8x7", format="png")

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

    workdir, sample_key, chrs = args
    chrs = chrs.split(",")
    hmm = CopyNumberHMM(workdir=workdir)
    hmm.plot(sample_key, chrs=chrs)

    image_name = sample_key + "_cn." + iopts.format
    savefig(image_name, dpi=iopts.dpi, iopts=iopts)
%prog plot workdir sample chr1,chr2

    Plot some chromosomes for visual proof. Separate multiple chromosomes with
    comma. Must contain folder workdir/sample-cn/.