custom neon animation behavior...not working

neonAnimationBehavior.js

<link rel="import" href="../../bower_components/polymer/polymer.html">
<link rel="import" href="../../bower_components/neon-animation/neon-animation-behavior.html">
<!-- <link rel="import" href="../../bower_components/web-animations-js/web-animations.html"> -->
/*
grow-width-animation
config: {
  node:<the node to operate on>
  width: <string> the width in pixels to end on.
}
 */

<dom-module id="grow-width-animation">
    <script>
    (function(){

      Polymer({
        is:'grow-width-animation',
        behaviors: [
          Polymer.NeonAnimationBehavior
        ],
        configure: function(config) {
          var node = config.node;
        
          this._effect = new KeyframeEffect(node, [
           {'width': '0px'},
           {'width': config.width}
         ], this.timingFromConfig(config));
         return this._effect;
       }
     });
    }());
    </script>
  </dom-module>