def set_port_policy(self, port, policy):
        port_id = port['port_id']
        old_policy = self.get_port_policy(port)
        self.known_policies[policy.id] = policy
        self.port_policies[port_id] = policy.id
        self.qos_policy_ports[policy.id][port_id] = port
        if old_policy and old_policy.id != policy.id:
            del self.qos_policy_ports[old_policy.id][port_id]
        return old_policy
Attach a port to policy and return any previous policy on port.
dataset/ETHPy150Open openstack/neutron/neutron/agent/l2/extensions/qos.py/PortPolicyMap.set_port_policy