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
product/gradle-plugin/src/main/python/pip/_vendor/ipaddress.py