CIImage says `Cannot render image (with an input Metal texture) using a metal context.`

Question

I am attempting to convert a MTLTexture to a CGImage by adding an extension function to MTLTexture objects inside of my macOS playground.

The current function looks like this:

extension MTLTexture {
    func toImage() -> CGImage? {
        let context = CIContext()
        let texture = self
        let cImg = CIImage(mtlTexture: texture, options: nil)!
        let cgImg = context.createCGImage(cImg, from: cImg.extent)!
        return cgImg
    }
}

However the line that is supposed to initialize cImg causes the concole to print Cannot render image (with an input Metal texture) using a metal context. and return nil.

Why is this happening and how can I fix it?