- ingress_ports = map(lambda port_pair: port_pair.ingress, port_pair_chain)
- egress_ports = map(lambda port_pair: port_pair.ingress, port_pair_chain)
+ ingress_ports = list(map(lambda port_pair: port_pair.ingress, port_pair_chain))
+ egress_ports = list(map(lambda port_pair: port_pair.ingress, port_pair_chain))