Labels support string[] and string[][]

As seen here http://www.chartjs.org/samples/latest/scales/multiline-labels.html. [source, see line 29](view-source:http://www.chartjs.org/samples/latest/scales/multiline-labels.html).

types/chart.js/index.d.ts

@@ -130,7 +130,7 @@ declare namespace Chart {
     }
 
     interface ChartData {
-        labels?: string[];
+        labels?: string[] | string[][];
         datasets?: ChartDataSets[];
     }