如何删除多维数组中的唯一元素？

def delete_unique_elements(arr):
    # 统计元素出现次数
    count = {}
    for item in arr:
        if isinstance(item, list):  # 判断是否为多维数组的子数组
            delete_unique_elements(item)
        else:
            count[item] = count.get(item, 0) + 1

    # 找到唯一元素并删除
    unique_elements = [key for key, value in count.items() if value == 1]
    for item in arr:
        if isinstance(item, list):
            item[:] = [x for x in item if x not in unique_elements]
        else:
            if item in unique_elements:
                arr.remove(item)

# 示例用法
my_array = [[1, 2, 3], [4, 5, 6], [1, 2, 3], [7, 8, 9]]
delete_unique_elements(my_array)
print(my_array)  # 输出：[[1, 2, 3], [1, 2, 3]]