def merylhistogram(merylfile):
    """
    Run meryl to dump histogram to be used in kmer.histogram(). The merylfile
    are the files ending in .mcidx or .mcdat.
    """
    pf, sf = op.splitext(merylfile)
    outfile = pf + ".histogram"
    if need_update(merylfile, outfile):
        cmd = "meryl -Dh -s {0}".format(pf)
        sh(cmd, outfile=outfile)

    return outfile
Run meryl to dump histogram to be used in kmer.histogram(). The merylfile
    are the files ending in .mcidx or .mcdat.