Data duplication in list when reading from NETCONF using RESTCONF

A request was sent:

GET
http://localhost:8080/restconf/config/opendaylight-inventory:nodes/node/XY_NODE/yang-ext:mount/XY-path/foo

<foo
xmlns="xy:z">
<bar>
<bar-key>191</bar-key>
<item>
<item-key>permit ip host 10.0.0.1 host 10.0.0.2</item-key>
</item>
<item>
<item-key> permit ip host 10.0.0.1 host 10.0.0.2</item-key>
</item>
</bar>
</foo>

Data were received through NETCONF with no duplication. In corresponding YANG model, item-key was defined as key of item.