Autocomplete: widget method not documented

Saw a post from Rich where he suggested someone use the widget method in autocomplete.

open: function( event, ui ) {

$( this ).autocomplete( "widget" )

.find( "ui-menu-item-alternate" )

.removeClass( "ui-menu-item-alternate" )

.end()

.find( "li.ui-menu-item:odd a" )

.addClass( "ui-menu-item-alternate" );

}

Link: http://forum.jquery.com/topic/alternating-style-on-autocomplete#14737000000779882

I can not find documentation on autocomplete for the widget method.