Sorting Elements of an Array by Frequency

class Solution:
    def frequencySort(self, nums: List[int]) -> List[int]:
        dict={}
        for i in nums:
            dict[i]=dict.get(i,0)+1
        arr=[[v,k] for k,v in dict.items()]
        arr.sort(key=lambda x: (x[0],-x[1]))
        ans=[]
        for v,k in arr:
            for j in range(v):
                ans.append(k)
        return ans