Occurs before an item becomes collapsed.
|e||Object||An event object which contains the collapsing item|
This event can be handled by creating a function in your application controller $scope and applying this function as value to an attribute in TreeView directive:
The events attribute has a higher priority than the before-collapse attribute. If both attributes are set, the value from events attribute is used.
For cancellation, simply return a false value in this event handler.
Supported in: v1.0.