How to add/change the ease method to a SlideUp() or SlideDown() function

How to add/change the ease method to a SlideUp() or SlideDown() function

Hi, I'm new to the forum. I've taken time to search through the forum on the look-out for a similar topic, but have not found one. I would like to add or change the slide effect by adding a easeInExpo to a SlideUp() or SlideDown() function
  1.         jQuery(function( $ ){
  2.                   var container = $( "#container" );

  4.             $( "a" ).click(function( event ){
  5.                     event.preventDefault();
  6.                     if (container.is( ":visible" )){

  8.                         container.slideUp( 500 )
  9.                     } else {
  10.                         container.slideDown( 500 );
  11.                     }
  12.                 }
  13.             );
  14.         });
  15.     </script>
I tried to add the easing by doing this

  1.                         container.slideUp( "slow", "easeInExpo" )
  2.                     } else {
  3.                         container.slideDown( "slow",  "easeInExpo" );

but it did not work. A workaround to this was using a plugin
Using that plugin, I can do things like
  1.          $ ( container ). slideUp ({ 
     duration: 500, easing: easeInExpo, complete: callback});
Easy, but this does not help me understand how it works.

I think I may need to use slideToggle() because slide Up and Down may have their own default easing. I need help to achieve this easeInExpo effect when the container div pops up and down.

How do I achieve this?

See my jQuery example  here

Thank-you.