def createRegionStr(chr, start, end=None):
    """
    Creating "samtools"-style region string such as
    "chrN:zzz,zzz,zzz-yyy,yyy,yyy". If end is not specified,
    it will create "chrN:xxx,xxx,xxx-xxx,xxx,xxx".
    :param chr:
    :param start:
    :param end:
    :return: A string of samtool-style region
    """
    if end == None:
        return str(chr) + ":" + str(int(start)) + "-" + str(int(start))
    elif end is not None:
        return str(chr) + ":" + str(int(start)) + "-" + str(int(end))