Swift: How to suppress callout for user location

suppressCallout.swift

func mapView(mapView: MKMapView!, viewForAnnotation annotation: MKAnnotation!) -> MKAnnotationView!{
    // user location
    if annotation is MKUserLocation {
        (annotation as! MKUserLocation).title = ""
        // use blue pulsy instead of pin
        return nil
    }
    // other pins
    return mapView.dequeueReusableAnnotationViewWithIdentifier("pin") as? MKPinAnnotationView
}