Write first_repeat(items) returning the first value that appears for the second time while scanning left to right, or None.
first_repeat([2, 5, 1, 2, 3, 5]) → 2
first_repeat([1, 2, 3]) → None
Submit runs 4 tests, including hidden edge cases.
Each hint gives a little more help. Try on your own first.
Run your code to see the output here.