docs: function ChartGauge () {
      var gaugeLinker = function (scope, element, attrs, chartCtrl) {
          var gauge = {};
          if (attrs.min) {
              gauge.min = parseInt(attrs.min);
          }
          if (attrs.max) {
              gauge.max = parseInt(attrs.max);
          }
          if (attrs.width) {
              gauge.width = parseInt(attrs.width);
          }
          if (attrs.units) {
              gauge.units = attrs.units
          }
          if (attrs.showLabel) {
              gauge.label = {"show": (attrs.showLabel === 'true')};
          }
          if (attrs.expand) {
              gauge.expand = (attrs.expand === 'true');
          }
          chartCtrl.addGauge(gauge);
          if (attrs.labelFormatFunction) {
              chartCtrl.addGaugeLabelFormatFunction(scope.labelFormatFunction());
          }
      };
  
      return {
          require: '^c3chart',
          restrict: 'E',
          scope: {
              'labelFormatFunction': "&"
          },
          replace: true,
          link: gaugeLinker
      };
  }