A collection containing a maximum of 2 RouteLabel instances for the route. It will return an empty list if no labels are available. The main street names or route numbers through which the route is going to pass that differentiate it from other alternatives routes. The labels are ordered by importance based on how much time the route spends on each road segment, not by traversal sequence. This helps users quickly identify and distinguish between different route alternatives when alternative routes have been quested via RouteOptions. Gets route labels.