Create prepped reference directory for pisces.

    Requires a custom GenomeSize.xml file present.

def _prep_genome(out_dir, data):
    """Create prepped reference directory for pisces.

    Requires a custom GenomeSize.xml file present.
    """
    genome_name = utils.splitext_plus(os.path.basename(dd.get_ref_file(data)))[0]
    out_dir = utils.safe_makedir(os.path.join(out_dir, genome_name))
    ref_file = dd.get_ref_file(data)
    utils.symlink_plus(ref_file, os.path.join(out_dir, os.path.basename(ref_file)))
    with open(os.path.join(out_dir, "GenomeSize.xml"), "w") as out_handle:
        out_handle.write('<sequenceSizes genomeName="%s">' % genome_name)
        for c in pysam.AlignmentFile("%s.dict" % utils.splitext_plus(ref_file)[0]).header["SQ"]:
            cur_ploidy = ploidy.get_ploidy([data], region=[c["SN"]])
            out_handle.write('<chromosome fileName="%s" contigName="%s" totalBases="%s" knownBases="%s" '
                             'isCircular="false" ploidy="%s" md5="%s"/>' %
                             (os.path.basename(ref_file), c["SN"], c["LN"], c["LN"], cur_ploidy, c["M5"]))
        out_handle.write('</sequenceSizes>')
    return out_dir