In iOS/Swift, at runtime how do you actually get just the full path of an image in the project?

Question

Say you use ...

let x = UIImage(named: "example.jpg")

UIImage "knows" how to find the image "example.jpg"

But say you are using, for example,

let y = CGDataProvider(filename: ...)

In fact, "example.jpg" won't work. You need the full path.

What is it that UIImage#named does to convert "example.jpg" to the full path; how can we do that?