code: function _initHideAnimation(item, prevItem, size) {
          var startHideAnimation = _startHideAnimation.bind(this, item, prevItem, size);
          if (item.wait) {
              item.wait.then(startHideAnimation, startHideAnimation);
          }
          else {
              startHideAnimation();
          }
      }
docs: Waits for the animation to start.