code: function (index, datasetIndex) {
        var me = this;
        var label = me.chart.data.labels && index < me.chart.data.labels.length ? me.chart.data.labels[index] : '';
  
        if (typeof me.chart.data.datasets[datasetIndex].data[0] === 'object') {
          if (me.isHorizontal()) {
            label = me.chart.data.datasets[datasetIndex].data[index].x;
          } else {
            label = me.chart.data.datasets[datasetIndex].data[index].y;
          }
        }
  
        return prettyPrintDuration(me.parseDuration(label));
      }
docs: Get tooltip label