I need help with a simple function.  This function is taken from a Tableau API example.

function yearFilter(year) {

var sheet = viz.getWorkbook().getActiveSheet();

if (year === "") { sheet.clearFilterAsync("Academic Year");

} else {

sheet.applyFilterAsync("Academic Year", year, tableau.FilterUpdateType.REPLACE);

}

};

It does not work with a dashboard.  I get the following error message:

     TypeError: sheet.applyFilterAsync is not a function. (In 'sheet.applyFilterAsync("Investment", investment, tableau.FilterUpdateType.REPLACE)', 'sheet.applyFilterAsync' is undefined)

How do I modify this function to work with a dashboard. 

Thanks