code: function (previousHand) {
      var controlConfiguration;
      var el = this.el;
      var hand = this.data;
      var self = this;
  
      // Get common configuration to abstract different vendor controls.
      controlConfiguration = {
        hand: hand,
        model: false,
        orientationOffset: {x: 0, y: 0, z: hand === 'left' ? 90 : -90}
      };
  
      // Set model.
      if (hand !== previousHand) {
        this.loader.load(MODEL_URLS[hand], function (gltf) {
          var mesh = gltf.scene.children[0];
          mesh.mixer = new THREE.AnimationMixer(mesh);
          self.clips = gltf.animations;
          el.setObject3D('mesh', mesh);
          mesh.position.set(0, 0, 0);
          mesh.rotation.set(0, 0, 0);
          el.setAttribute('vive-controls', controlConfiguration);
          el.setAttribute('oculus-touch-controls', controlConfiguration);
          el.setAttribute('windows-motion-controls', controlConfiguration);
        });
      }
    }
docs: Update handler. More like the `init` handler since the only property is the hand, and
  that won't be changing much.