Queue list for a node connector is always empty

1. add queue for a port using mininet:

sudo ovs−vsctl −− set port s1-eth1 qos=@newqos −− −−id=@newqos create qos type=linux−htb other−config:max−rate=1000000 queues:0=@newqueue −− −−id=@newqueue create queue other−config:min−rate=1000000 other−config:max−rate=1000000

2. read queue operational data as shown below, queue list is always empty.
InstanceIdentifier<FlowCapableNodeConnector> connectorRef = InstanceIdentifier.builder(Nodes.class)
.child(Node.class, nodeKey).child(NodeConnector.class, nodeConnectorKey)
.augmentation(FlowCapableNodeConnector.class).toInstance();

FlowCapableNodeConnector nodeConnector =
(FlowCapableNodeConnector) dataProviderService.readOperationalData(connectorRef);

List<Queue> queueList = nodeConnector.getQueue();

queueList is always empty.

3. we are able to see queue stats using REST API
http://localhost:8080/restconf/operational/opendaylight-inventory:nodes/node/openflow:1/node-connector/openflow:1:1/

{
"node-connector": [
{
"flow-node-inventory:current-feature": "copper 10gb-fd",
"flow-node-inventory:hardware-address": "0E:52:5A:55:C0:47",
"flow-node-inventory:peer-features": "",
"id": "openflow:1:1",
"flow-node-inventory:state":

{ "flow-node-inventory:blocked": false, "flow-node-inventory:link-down": false, "flow-node-inventory:live": false }

,
"flow-node-inventory:configuration": "",
"opendaylight-port-statistics:flow-capable-node-connector-statistics": {
"opendaylight-port-statistics:receive-over-run-error": 0,
"opendaylight-port-statistics:transmit-errors": 0,
"opendaylight-port-statistics:receive-drops": 0,
"opendaylight-port-statistics:receive-crc-error": 0,
"opendaylight-port-statistics:duration": {},
"opendaylight-port-statistics:packets":

{ "opendaylight-port-statistics:transmitted": 774, "opendaylight-port-statistics:received": 5 }

,
"opendaylight-port-statistics:receive-frame-error": 0,
"opendaylight-port-statistics:receive-errors": 0,
"opendaylight-port-statistics:transmit-drops": 0,
"opendaylight-port-statistics:bytes":

{ "opendaylight-port-statistics:transmitted": 48762, "opendaylight-port-statistics:received": 378 }

,
"opendaylight-port-statistics:collision-count": 0
},
"flow-node-inventory:port-number": 1,
"flow-node-inventory:supported": "",
"flow-node-inventory:advertised-features": "",
"flow-node-inventory:name": "s1-eth1",
"flow-node-inventory:queue": [
{
"flow-node-inventory:queue-id": 0,
"opendaylight-queue-statistics:flow-capable-node-connector-queue-statistics": {
"opendaylight-queue-statistics:duration": {},
"opendaylight-queue-statistics:transmitted-bytes": 45360,
"opendaylight-queue-statistics:transmitted-packets": 720,
"opendaylight-queue-statistics:transmission-errors": 0
}
}
]
}
]
}