Where can I find DispatchQueue.main

Hello
I am trying to implement this example
but it requires a call to a method :

AVCaptureMetadataOutput.setMetadataObjectsDelegate

Which requires DispatchQueue as second argument.
The example uses DispatchQueue.main which as far as my little understanding of this
returns the DispatchQueue of the app’s main thread.

Thanks

Globals.dispatch_get_main_queue()