How to use the @accordproject/concerto-core.ModelLoader.loadModelManager function in @accordproject/concerto-core

static async compile(target, ctoSystemFile, ctoFiles, output) {
        const modelManager = await ModelLoader.loadModelManager(ctoSystemFile, ctoFiles);

        let visitor = null;

        switch(target) {
        case 'Go':
            visitor = new GoLangVisitor();
            break;
        case 'PlantUML':
            visitor = new PlantUMLVisitor();
            break;
        case 'Typescript':
            visitor = new TypescriptVisitor();
            break;
        case 'Java':
            visitor = new JavaVisitor();
            break;

static async validate(sample, ctoSystemFile, ctoFiles) {
        const json = JSON.parse(fs.readFileSync(sample, 'utf8'));

        const modelManager = await ModelLoader.loadModelManager(ctoSystemFile, ctoFiles);
        const factory = new Factory(modelManager);
        const serializer = new Serializer(factory, modelManager);

        const object = serializer.fromJSON(json);
        return JSON.stringify(serializer.toJSON(object));
    }

static async get(ctoSystemFile, ctoFiles, output) {
        const modelManager = await ModelLoader.loadModelManager(ctoSystemFile, ctoFiles);
        mkdirp.sync(output);
        modelManager.writeModelsToFileSystem(output);
        return `Loaded external models in '${output}'.`;
    }
}