pop_at(items, index) that removes and returns the element at index using .pop(), then returns a tuple (popped_value, remaining_list). Assume index is always valid.items = [5, 10, 15, 20], index = 1
(10, [5, 15, 20])
.pop(1) removes and returns 10, leaving the rest.
list.pop(index) both removes and returns the value.