Change a labels for tag using Prototype?

Question

I know I can change a labels id like this:

$(someid).id = 123;

How can I change the for, too?

This is the code I have:

<label id="10" for="xyz">
   sometext
</label>

How can I change the for from xyz to abc using Prototype?

Thanks :)

Answer 1

$(someid).writeAttribute('for', 'abc');