Incorrect response when using 'is_netmask` with inverse netmask.

[jdrew82]

Environment

• Python version: 3.11
• netutils version: 1.9.0

Expected Behavior

Expected to get a True response when passing "0.31.255.255" to is_netmask().

Observed Behavior

It was returned as False:

In [1]: from netutils.ip import is_netmask

In [2]: is_netmask("0.31.255.255")
Out[2]: False

Steps to Reproduce

1. Import is_netmask() in REPL.
2. Pass inverse/wildcard netmasks to the is_netmask().
3. See results.

[jdrew82]

This also means the netmask_to_cidr() function doesn't work as the is_netmask() returns False. If you test what's returned with that function ignoring the is_netmask() check you get the CIDR returned when using an inverse netmask.