@Override
    public List<Node> usedComponents() {
        if (arguments == null) {
            throw new IllegalStateException("Arguments must be set first.");
        }
        List<Node> ret = new ArrayList<>();
        for (Object arg : arguments) {
            if (arg instanceof Node) {
                ret.add((Node) arg);
            }
        }
        return ret;
    }
@author Tony Vaagenes
@author gjoranv
@author ollivir
container-core/src/main/java/com/yahoo/container/di/componentgraph/core/ComponentNode.java