         **Discussion:** By default, non-mixable streams are returned, however, these can be filtered 
         out by setting `includeNonMixable` to `false`.
 
-        - Returns: An array of `AudioStreamBasicDescription`
+        - Returns: *(optional)* An array of `AudioStreamBasicDescription`
      */
     public final func availablePhysicalFormatsMatchingCurrentNominalSampleRate(includeNonMixable: Bool = true) -> [AudioStreamBasicDescription]? {
         guard let physicalFormats = availablePhysicalFormats,

        Returns a `UInt32` that specifies the first element in the owning device that corresponds to
        element one of this stream.

        - Returns: A `UInt32`
     */
    public lazy var startingChannel: UInt32? = {
        var address = AudioObjectPropertyAddress(

        For output streams, and to continue using the same `Direction` concept used by `AMCoreAudioDevice`,
        this will be `Direction.Playback`, likewise, for input streams, `Direction.Recording` will be returned.

        - Returns: *(optional)* A `Direction`
     */
    public lazy var direction: Direction? = {
        var address = AudioObjectPropertyAddress(
