We cannot access (read or modify) a list item of list which key's type is instance identifier.
Steps to reproduce:
Create a new resource as defined in NETCONF-1264 and invoke (you can use POST for the whole container in case NETCONF-1264 is not fixed yet):
GET http://192.168.56.25:8181/rests/data/network-topology:network-topology/topology=topology-netconf/node=17830-sim-device/yang-ext:mount/car-purchase:persons/person=%2Fpeople%3Apeople%2Fperson%5Bid%3D%270%27%5D