def get_mtu(self, physical_network=None):
        mtu = super(GreTypeDriver, self).get_mtu(physical_network)
        return p_const.GRE_ENCAP_OVERHEAD - mtu if mtu else 0
dataset/ETHPy150Open openstack/neutron/neutron/plugins/ml2/drivers/type_gre.py/GreTypeDriver.get_mtu/swapped operands of `-`