   
   /**
    Add `output` to `captureSession`.
-   - Throws: `CaptureManagerError.InvalidCaptureOutput` if the output cannot be added to `captureSession`.
+   - Throws: `CaptureManagerError.invalidCaptureOutput` if the output cannot be added to `captureSession`.
    */
   fileprivate func addCaptureOutput(_ output: AVCaptureOutput) throws {
     if (!captureSession.canAddOutput(output)) {

   - parameter outputs: A mask of options of type `CaptureSessionOutputs` indicating what outputs to add to the `AVCaptureSession`.
   - parameter errorHandler: A closure of type `(Error) -> Void`. Called on the **main thread** if anything performed inside of `sessionQueue` thread throws an error.
   
   - Throws: `CaptureManagerError.InvalidSessionPreset` if `sessionPreset` is not valid.
   */
  public func setUp(sessionPreset: String,
                  previewLayerProvider: VideoPreviewLayerProvider?,

  
  /**
   Add `input` to `captureSession`.
   - Throws: `CaptureManagerError.invalidCaptureInput` if the input cannot be added to `captureSession`.
   */
  fileprivate func addCaptureInput(_ input: AVCaptureInput) throws {
    if (!captureSession.canAddInput(input)) {
