1748. Sum of Unique Elements - LeetCode Solution

class Solution:
    def sumOfUnique(self, nums: List[int]) -> int:
        a = {}
        
        for i in nums:
            if i in a:
                a[i] +=1
            else:
                a[i] =1
        
        d = 0
        for i in a:
            if a[i] == 1:
                d+=i
        
        return d