How to get the next level data for a hierarchical dimension?

[Anonymous]

I am writing a stacked group d3 extension which accepts a hierarchical dimension (Country> brand> mixture) and year dimension and three measures (spend, maco,volume). The extension works fine for a normal country dimension but i want it to drill down for the hierarchical dimension, i.e; when I click on the country label, it should get the brands for that country and repaint the chart. Similarly when i click on the brand it should get the mixtures for that brand.

I am confused as to what should go as a parameter to the backendApi.selectvalues() function.I have the dinKeys for each object.