If NETCONF device provide response with augmented ietf-netconf-monitoring data, there is an only way how to create device EffectiveModelContext by adding required device models to cache/schema.

Due to unknown elements in response and default `strictParsing` set to true inside XmlParserStream:
https://github.com/opendaylight/netconf/blob/master/netconf/netconf-util/src/main/java/org/opendaylight/netconf/util/NetconfUtil.java#L408

variable providedSources will be empty:
https://github.com/opendaylight/netconf/blob/master/netconf/sal-netconf-connector/src/main/java/org/opendaylight/netconf/sal/connect/netconf/DeviceSourcesResolver.java#L56

And if device models are not available in cache/schema, this part will fail because no models will be provided:
https://github.com/opendaylight/netconf/blob/master/netconf/sal-netconf-connector/src/main/java/org/opendaylight/netconf/sal/connect/netconf/NetconfDevice.java#L510

So device will be disconnected