剑指offer python版 找出数组中重复的数字

def aa(nums):
    if not nums:
        return False
    hashes={}
    ret=[]
    for s in nums:
        hashes[s]=hashes[s]+1 if hashes.get(s) else 1
        if hashes[s] >1:
            ret.append(s)
            
    return list(set(ret))


print(aa([1,2,3,4,4,2,2,3]))