Usage of ietf-network-topology tp-ref doesn't validate in pyang

pyang-errors.txt

topo-client.yang:5: warning: imported module ietf-network not used
topo-client.yang:15 (at topo-client.yang:23): error: the key "net:network-ref" does not reference an existing leaf
[email protected]:78: error: ietf-network:network-ref in the path for tp-ref at topo-client.yang:15 (at [email protected]:74) is not found
[email protected]:42: error: topo-client:network in the path for network-ref at topo-client.yang:15 (at [email protected]:40) is not found
[email protected]:56: error: topo-client:network in the path for node-ref at topo-client.yang:15 (at [email protected]:53) is not found

topo-client.yang

module topo-client {
  namespace "urn:test:topo-client";
  prefix tc;

  import ietf-network {
    prefix net;
  }

  import ietf-network-topology {
    prefix topo;
  }

  list service-end-point {
    key 'id';
    uses service-end-point;
  }

  grouping service-end-point {
    leaf id {
      type string;
    }
    list mapped-topo-end-point {
      key "net:network-ref net:node-ref topo:tp-ref";
      uses topo:tp-ref;
    }
  }
}