def roc_file_to_string(roc_fn, inner_sep=':', outer_sep=';'):
    """ Convert a file with a ROC table into a string with one line per ROC row """
    fields = []
    with open(roc_fn) as fh:
        for ln in fh:
            cor, _, _, incor, mapq, _, _, _, _, _ = ln.rstrip().split(',')
            if mapq == "mapq":
                continue
            fields.append(inner_sep.join([mapq, cor, incor]))
    return outer_sep.join(fields)