如何在Mapbox iOS SDK中删除折线？

let coordinates = [
    CLLocationCoordinate2D(latitude: 37.7749, longitude: -122.4194),
    CLLocationCoordinate2D(latitude: 34.0522, longitude: -118.2437),
    CLLocationCoordinate2D(latitude: 32.7157, longitude: -117.1611)
]
let polyline = MGLPolyline(coordinates: coordinates, count: UInt(coordinates.count))
mapView.addAnnotation(polyline)

for annotation in mapView.annotations ?? [] {
    if let polyline = annotation as? MGLPolyline {
        mapView.removeAnnotation(polyline)
    }
}