I just tried it, and it was trivial to do in a minute or two on my laptop. However, I did took note of two syntax mistakes that I made in the python REPL that were immediately obvious there and took seconds to fix, but which I most likely would not have noticed on a whiteboard.
So there's quite a bunch of problems where if the acceptable "format" of the answer is "hey, I'll just pull out my laptop from the backpack and push the solution to github in 15 minutes" then it'd be okay, but it'd be hard to do it while 'whiteboarding' without access to immediate feedback and easily accessible API documentation.
For example, I work in many languages, and for many APIs I can't remember whether in this particular language the same thing is called add or append or something else; e.g. I've worked on Java code for a dozen years and would be a quite productive Java developer, but since I haven't written any new code in Java for quite some time recently, I can't remember off of my head what's the right boilerplate to open a text file for reading in Java - it's something that a Java tutorial might have in the first pages right after Hello world, but I'd still have to look up the incantation to pass the encoding properly - there's like three Reader classes to instantiate and I don't recall their names off the top of my head.