def _split_optional_netmask(address):
    """Helper to split the netmask and raise AddressValueError if needed"""
    addr = _compat_str(address).split('/')
    if len(addr) > 2:
        raise AddressValueError("Only one '/' permitted in %r" % address)
    return addr
Helper to split the netmask and raise AddressValueError if needed
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_vendor/ipaddress.py