在字典数组中获取重复值。迅速

I have an array like this

我有这样的数组

[
    ["itm_id": 4, "itm_name": Chicken],
    ["itm_id": 4, "itm_name": Chicken],
    ["itm_id": 4, "itm_name": Chicken],
    ["itm_id": 7, "itm_name": Cat]
]
[
    ["i