src/charts/grouped-bar.js
function buildLayers() {
            layers = transformedData.map((item) => {
                let ret = {};

                groups.forEach((key) => {
                    ret[key] = item[key];
                });

                return assign({}, item, ret);
            });
        }
function buildLayers() {
            layers = transformedData.map((item) => {
                let ret = {};

                groups.forEach((key) => {
                    ret[key] = item[key];
                });

                return assign({}, item, ret);
            });
        }
function buildLayers ( ) { layers = transformedData . map ( ( item ) => { let ret = { } ; groups . forEach ( ( key ) => { ret [ key ] = item [ key ] ; } ) ; return assign ( { } , item , ret ) ; } ) ; }
Builds the grouped layers layout
@return {D3Layout} Layout for drawing the chart
@private
Builds the grouped layers layout