Google Charts- How to map the data of entity to widget to display pie chart?

Hi, I am trying to display a pie chart. For this I created an entity with the name Data which consists of three attributes. Now in my page I have placed a dataview mapped to the entity and then placed the Google Pie Chart widget inside it. So now when trying to map the entity in data source of the widget, it is taking only a single attribute. When I run the app it is showing "table has no columns". I have searched for an example for using the Google charts. But I didn't get how to map data to widget. Could anyone please help me how to do this. Thanks
1 answers

If you go to Github and download this project you have a working example in the Test directory when you unzip the package.