[How to?] adding a slow expanding effect on this code

[How to?] adding a slow expanding effect on this code

I found this code and it works, but I don't know to expand it with some expandin slow effect, because there's no indication that the code is expanding the table, is that the slideToggle that does the expanding? thanks for your time

var $headers = $('.header').click(function () {
    $(this).find('span').text(function (_, value) {
        return value == '-' ? '+' : '-'
    });
    $(this).nextUntil('tr.header').slideToggle(100, function () {});
});