val referenceLayers: MutableList<Layer>
The collection of reference layers in this basemap. Reference layers are drawn on top all other layers in the ArcGISMap or ArcGISScene to display information such as boundaries, labels, and traffic networks. The collection can be empty but it is never null.
This collection is specific to this basemap so you cannot reuse a collection coming from another Basemap.
List Impl. Mutable List Impl