Same items, any order

Two lists hold item names, possibly with repeats and in any order. Write same_items(a, b) that returns True if they contain the same set of distinct items.

same_items(["apple", "milk", "apple"], ["milk", "apple"])  ->  True
same_items(["apple"], ["apple", "milk"])                   ->  False

def same_items(a, b):
    ...