Converts a prefix length to a dotted decimal subnet mask

    Args:
        prefixlen (str): The prefix length value to convert

    Returns:
        str: The subt mask as a dotted decimal string

def prefixlen_to_mask(prefixlen):
    """Converts a prefix length to a dotted decimal subnet mask

    Args:
        prefixlen (str): The prefix length value to convert

    Returns:
        str: The subt mask as a dotted decimal string
    """
    prefixlen = prefixlen or '32'
    addr = '0.0.0.0/%s' % prefixlen
    return str(netaddr.IPNetwork(addr).netmask)