How to use the jsdoctypeparser.Builder.GenericType function in jsdoctypeparser

}
                return _iterateDocTypes(subnode, cb);
            }) || [];
            if (node.nullable) {
                var subnode = {typeName: 'null', collectionNode: node};
                res.concat(cb(subnode));
            }
            break;

        case node instanceof TypeBuilder.TypeName:
            // name: string
            node.typeName = node.name;
            res = cb(node);
            break;

        case node instanceof TypeBuilder.GenericType:
            // genericTypeName: string,
            // parameterTypeUnions: Array.
            node.typeName = node.genericTypeName.type;
            res = cb(node) || [];
            if (node.parameterTypeUnions) {
                // node.parameterTypeUnions.collectionNode = node;
                res.concat(node.parameterTypeUnions.map(function(subnode) {
                    subnode.parentElement = node;
                    _iterateDocTypes(subnode, cb);
                }));
            }
            break;

        case node instanceof TypeBuilder.FunctionType:
            // parameterTypeUnions: Array.,
            // returnTypeUnion: TypeUnion|null,