docs: function ChartBar() {
      var barLinker = function (scope, element, attrs, chartCtrl) {
          var bar = {};
          if (attrs.width) {
              bar.width = parseInt(attrs.width);
          }
          if (attrs.ratio) {
              if (!bar.width) {
                  bar.width = {};
              }
              bar.width.ratio = parseFloat(attrs.ratio);
          }
          if (attrs.zerobased) {
              bar.zerobased = (attrs.zerobased === 'true');
          }
          chartCtrl.addBar(bar);
      };
  
      return {
          require: '^c3chart',
          restrict: 'E',
          scope: {},
          replace: true,
          link: barLinker
      };
  }