def _is_valid_netmask(self, prefixlen):
        try:
            prefixlen = int(prefixlen)
        except ValueError:
            return False
        return 0 <= prefixlen <= self._max_prefixlen
Verify that the netmask/prefixlen is valid.
dataset/ETHPy150Open uwdata/termite-data-server/web2py/gluon/contrib/ipaddr.py/IPv6Interface._is_valid_netmask