     public func clockSourceNames(channel: UInt32, direction: Direction) -> [String]? {
 
         if let clockSourceIDs = clockSourceIDs(channel: channel, direction: direction) {
-            return clockSourceIDs.map { (clockSourceID) -> String in
+            return clockSourceIDs.map {
                 // We expect clockSourceNameForClockSourceID to never fail in this case, 
                 // but in the unlikely case it does, we provide a default value.
-                clockSourceName(clockSourceID: clockSourceID) ?? "Clock source \(clockSourceID)"
+                clockSourceName(clockSourceID: $0) ?? "Clock source \(clockSourceID)"
             }
         }
 

        let status = getPropertyDataArray(address, value: &relatedDevices, andDefaultValue: AudioDeviceID())

        if noErr == status {
            return relatedDevices.map { deviceID -> AudioDevice? in
                AudioDevice.lookup(by: deviceID)
            }.flatMap { $0 }
        }

        return nil

     
        - Parameter deviceID: An audio device identifier that is valid and present in the system.
     */
    private init?(id: AudioObjectID) {

        super.init(objectID: id)

        guard owningObject != nil else { return nil }

