we use 600 here to ensure that the directive is caught before others
function(scope, $element, attrs, ctrl, $transclude) {
      var previousElement, previousScope;
      scope.$watchCollection(attrs.ngAnimateSwap || attrs['for'], function(value) {
        if (previousElement) {
          $animate.leave(previousElement);
        }
        if (previousScope) {
          previousScope.$destroy();
          previousScope = null;
        }
        if (value || value === 0) {
          $transclude(function(clone, childScope) {
            previousElement = clone;
            previousScope = childScope;
            $animate.enter(clone, null, $element);
          });
        }
      });
    }