Down Then Back Up

Write bounce(n: int) -> None that prints n, n - 1, down to 1 and then 1, 2, back up to n, one number per line, using a single recursive function: when n is 0 print nothing and return; otherwise print n, call the function with n - 1, and print n again after that call returns. The first print of each call happens on the way down and the second on the way back up as the calls finish. Do NOT write a main block or any top-level test code; the tests construct the calls. Input: one integer n, no prompt, which the tests read and pass to your function.