I have only found this solution.
[root@localhost ~]# ip netns exec qrouter-22366760-ae5e-4588-ba71-e8244f5f8fd8 route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 qr-70545ca6-4b
192.168.250.0 0.0.0.0 255.255.254.0 U 0 0 0 qg-cad8eab5-ef
0.0.0.0 192.168.250.1 0.0.0.0 UG 0 0 0 qg-cad8eab5-ef
[root@localhost ~]# ip netns exec qrouter-22366760-ae5e-4588-ba71-e8244f5f8fd8 ip route add 172.16.0.0/24 via 192.168.251.1
[root@localhost ~]# ip netns exec qrouter-22366760-ae5e-4588-ba71-e8244f5f8fd8 route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 qr-70545ca6-4b
172.16.0.0 192.168.251.1 255.255.255.0 UG 0 0 0 qg-cad8eab5-ef
192.168.250.0 0.0.0.0 255.255.254.0 U 0 0 0 qg-cad8eab5-ef
0.0.0.0 192.168.250.1 0.0.0.0 UG 0 0 0 qg-cad8eab5-ef
In vm:
$ traceroute 172.16.0.1
traceroute to 172.16.0.1 (172.16.0.1), 30 hops max, 46 byte packets
1 10.0.0.1 (10.0.0.1) 5.608 ms 1.185 ms 1.236 ms
2 192.168.251.1 (192.168.251.1) 1.553 ms 3.173 ms 3.191 ms
3 192.168.250.1 (192.168.250.1) 3.073 ms 1.732 ms 2.388 ms
4 195.208.117.190 (195.208.117.190) 74.664 ms 26.545 ms 93.563 ms