[racket] label-string

Hello friends,

how can I convert a vector  (define Vec #(1 2 3 4))

to a label-string to make a tab-panel??

I try this
(define tab-panel (new tab-panel%
                       (parent dialog)
                       (choices (vector->list Vec))))

but it fails due to contract violation: expected: label-string?

So what ist a label-string???


Yours,