Maybe, "... all combinations of its values are stripped from the beginning and end."

It is rather difficult to be both clear AND concise. Heck, I'm having trouble just trying to explain it.

Mark, that part is clear, but I think somehow reiterating how the method works would be helpful to someone who is only familiar with a handful of the string methods, knows strip() removes characters, sees that several characters can be specified, and assumes that all such characters will be removed.

As it is, it's sort of like a puzzle that's glaringly obvious once you figure it out, but frustrating in proportion to the amount of time spent figuring. Almost more trouble to figure out how to explain it without turning it into a tutorial than it is to sort it out on your own at the console.