Please add variable support sample code or doc

[tomjamescn]

Backend datasource plugin is very useful, great job! Thanks.

I’m developing a backend data source plugins according to the tutorial on offical tutorial build-a-data-source-backend-plugin

everything is ok, thanks the tutorial, but I have no idea how to add variables support for backend data source plugins, i found this official doc add-support-for-variables, but i don't know how to use, can you add sample code or doc in this simple-datasource-backend project?

thanks.

[tomjamescn]

applyTemplateVariables method in the latest grafana code can do this.