请问 tape 库中下面一段代码什么意思？

exports = module.exports = (function () {
    var harness;
    var lazyLoad = function () {
        return getHarness().apply(this, arguments);
    };
    
    lazyLoad.only = function () {
        return getHarness().only.apply(this, arguments);
    };
    
    lazyLoad.createStream = function (opts) {
        if (!opts) opts = {};
        if (!harness) {
            var output = through();
            getHarness({ stream: output, objectMode: opts.objectMode });
            return output;
        }
        return harness.createStream(opts);
    };
    
    return lazyLoad
    
    function getHarness (opts) {
        if (!opts) opts = {};
        opts.autoclose = !canEmitExit;
        if (!harness) harness = createExitHarness(opts);
        return harness;
    }
})();

exports.test = exports; // tap compat
exports.test.skip = Test.skip;