docs: function ChartColors () {
      var colorsLinker = function (scope, element, attrs, chartCtrl) {
          var pattern = attrs.colorPattern;
          if (pattern) {
              chartCtrl.addColorPatterns(pattern.split(","));
          }
  
          var thresholds = attrs.thresholds;
          if(thresholds){
              chartCtrl.addColorThresholds(thresholds.split(","));
          }
          
          if (attrs.colorFunction) {
              chartCtrl.addColorFunction(scope.colorFunction());
          }
      };
  
      return {
          "require": "^c3chart",
          "restrict": "E",
          "scope": {
              "colorFunction": "&"
          },
          "replace": true,
          "link": colorsLinker
      };
  }