Write flip_pairs(pairs) that returns a list where each pair (a, b) becomes (b, a).
flip_pairs([[1, 2], [3, 4]]) → [[2, 1], [4, 3]]
flip_pairs([]) → []
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.