Offline maps not working with mapbox plugin

QGeoTileSpec QGeoFileTileCacheMapbox::filenameToTileSpec(const QString &filename) const
{
    QStringList parts = filename.split('.');

    if (parts.length() != 2)
        return QGeoTileSpec();

        plugin: Plugin {
            id: plugin
            preferred: ["mapbox"]
            PluginParameter { name: "mapbox.access_token"; value: <myaccesstoken> }
            PluginParameter { name: "mapbox.map_id"; value: "project.handle" }
        }