code: function Selection () {
      var selectionLinker = function (scope, element, attrs, chartCtrl) {
          var enabled = attrs.enabled;
          var grouped = attrs.grouped;
          var multiple = attrs.multiple;
  
          if (enabled && enabled === 'true') {
              var selection = {"enabled": true};
              if (grouped && grouped === 'true') {
                  selection.grouped = true;
              }
              if (multiple && multiple === 'true') {
                  selection.multiple = true;
              }
              chartCtrl.addSelection(selection);
          }
      };
  
      return {
          "require": "^c3chart",
          "restrict": "E",
          "scope": {},
          "replace": true,
          "link": selectionLinker
      };
  }
docs: @ngdoc directive
  @name selection
  @description
  `selection` is used to to configure whether it is possible to select elements and interact with the chart to find selected elements.
  
  Restrict To:
  Element
  
  Parent Element:
  c3chart
  
  @param {String} enabled Specify whether the selection should be enabled or not, default is true.
  
  {@link http://c3js.org/reference.html#data-selection-enabled}
  
  @param {String} grouped Enables the grouped selection.
  
  {@link http://c3js.org/reference.html#data-selection-grouped}
  
  @param {String} multiple Enables possibility to select multiple items.
  
  {@link http://c3js.org/reference.html#data-selection-multiple}
  
  @example
  Usage:
  <selection enabled="true"/>
  Example:
  {@link http://jettro.github.io/c3-angular-directive/#examples}