code: function() {
          if (!this.playing) {
              return;
          }
          
          if (this.callbacks && this.callbacks.done) {
              this.callbacks.done.call(this, this.finish);
          }
          OpenLayers.Animation.stop(this.animationId);
          this.animationId = null;
          this.playing = false;
      }
docs: APIMethod: stop
  Stops the Tween, and calls the done callback
  Doesn't do anything if animation is already finished