How to use the download.default_directory function in download

static getChromeDownloadDirectory() {
        // .meteor/chimp_config.js configures chrome download dir relative to cwd()
        let chimpopts = require ('../../../.meteor/chimp_config');
        let downloadDir = chimpopts.webdriverio.desiredCapabilities.chromeOptions.prefs["download.default_directory"];
        expect(downloadDir, ".meteor/chimp_config.js must specify download.default_directory").to.be.ok;
        downloadDir = process.cwd() + "/" + downloadDir;
        return downloadDir;
    }