Thank you for the explanation, @sgugger!
So, when creating new classes you’re suggesting to use r###, correct?
In my experience most of the time r is used as a pattern in regex - that’s what I meant by a “regex string”. So I assumed it to be a regex thing  I understand this could be needed elsewhere when \ are to be treated literally. So, “raw” does make more sense. Thank you for this, @sgugger!