_require = function(parentId, module, callback) {
    if (typeof module === "string") {
        var payload = lookup(parentId, module);
        if (payload != undefined) {
            callback && callback();
            return payload;
        }
    } else if (Object.prototype.toString.call(module) === "[object Array]") {
        var params = [];
        for (var i = 0, l = module.length; i < l; ++i) {
            var dep = lookup(parentId, module[i]);
            if (dep == undefined && require.original)
                return;
            params.push(dep);
        }
        return callback && callback.apply(null, params) || true;
    }
}
Get at functionality define()ed using the function above