public static Map<String, ModelReference> toModelReferenceMap(Map<String, ModelNode> nodeMap) {
        Map<String, ModelReference> referenceMap = new LinkedHashMap<>();
        for (var entry : nodeMap.entrySet()) {
            referenceMap.put(entry.getKey(), entry.getValue().getModelReference());
        }
        return referenceMap;
    }
Represents a 'model' in a {@link ConfigInstance}.

@author bratseth
config-lib/src/main/java/com/yahoo/config/ModelNode.java