@Override
    public String toString() {
        var buf = new StringBuilder();
        buf.append(this.getClass().getName()).append(" containing: [");
        for (var id : registry.allComponentsById().keySet()) {
            buf.append(" ").append(id.toString());
        }
        buf.append(" ]");
        return buf.toString();
    }
factory for model-evaluation proxies
@author arnej
container-search/src/main/java/com/yahoo/search/ranking/RankProfilesEvaluatorFactory.java