jQuery slideDown with easing

How can use the slideDown() function with easing?

Maybe extend it somehow?

I'm looking for something like this:

jQuery.fn.slideDown = function(speed, easing, callback) {
  return ...
};

So i can use it slide this

$('.class').slideDown('400','easeInQuad');

or this

$('.class').slideDown('400','easeInQuad',function(){
   //callback
});