How to call a JavaScript function that is inside a "define" - anonymous method

How to call a function which is defined inside an anonymous function but both in the same JS file. Here is my code snippet. How to call _testMethodInside() from testMethodOutside()?

// Line 1 to 13 is an existing code from ESRI API
    define([
        "dojo/_base/declare",
        "dojo/_base/html"
    ], function (
        declare,
        html
    ) {
        return declare([_WidgetBase, _TemplatedMixin], {
            _testMethodInside: function () {
                return 'success';
            }
        });
    });

//Call above using this function
    function testMethodOutside(){
        //How to call _testMethodInside() function from here
    }

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