Returns the model layer object associated with the receiver, if any.
- iOS 2.0+
- macOS 10.5+
- tvOS 9.0+
- Core Animation
A layer instance representing the underlying model layer.
Calling this method on a layer in the presentation tree returns the corresponding layer object in the model tree. This method returns a value only when a transaction involving changes to the presentation layer is in progress. If no transaction is in progress, the results of calling this method are undefined.