Is there a Rails helper for "one, two and three"?

Sorry for such a trivial question, but it would be foolish for me to build this if it already existed.

I have a vague memory of having a Rails helper that can turn ['one', 'two', 'three']

into "one, two and three", but I could completely figure it out. And I can't figure out where in the API to look like it's not in the TextHelper module, and I can't figure out what to look for.

Does this method exist, or am I just imagining it?