JQuery UI Datepicker Extension Function

I would like the ability to add a custom function to an existing jquery class, similar to an extension method in C# (specifically datepicker).

I am able to get a static version of this working by declaring the below:

// declaration
$.ui.datepicker.hello = function () {
    alert('heya');
};

// caller
$.ui.datepicker.hello();

However as I am actually concerned with the specific instance of datepicker, I would much rathar be able to declare a function so I could do something like the below:

$("#date").datepicker.hello();
// Or
$("#date").datepicker("hello")

I have tried various methods including using jQuery.fn.extend() and the answers in add custom method to jquery ui dialog, but I get console errors stating "Object doesn't support this action" coming from jquery-ui.min.js when I attempt the accepted solution.

$.widget("ui.datepicker", $.ui.datepicker,{
    hello: function () {
        alert('yes');
    }
});

Is what I am trying to do even possible? Or is it just my execution that is lacking?