def is_netmask(self):
        int_val = (self._value ^ self._module.max_int) + 1
        return (int_val & (int_val - 1) == 0)
:return: ``True`` if this IP address network mask, ``False`` otherwise.
dataset/ETHPy150Open drkjam/netaddr/netaddr/ip/__init__.py/IPAddress.is_netmask