private List<ConfigInstance> usedConfigs() {
        if (availableConfigs == null) {
            throw new IllegalStateException("setAvailableConfigs must be called!");
        }
        List<ConfigInstance> ret = new ArrayList<>();
        for (Object arg : arguments) {
            if (arg instanceof ConfigKey<?>) {
                ret.add(getConfigInstance((ConfigKey<?>)arg));
            }
        }
        return ret;
    }
@author Tony Vaagenes
@author gjoranv
@author ollivir
container-core/src/main/java/com/yahoo/container/di/componentgraph/core/ComponentNode.java