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 Exa-Networks/exabgp/lib/exabgp/dep/ipaddress.py/IPv6Network._is_valid_netmask