Can you help me to determine its time complexity? - Leetcode Today POD

Round 1

Questions: Can you help determine its time complexity? (Accepted)
Q. Problem link - Max Sum of a Pair with Equal Sum of Digits

class Solution:
    # function for sum of digits of a number
    def checkDigitSum(self, n):
        total=0
        while n!=0:
            rem=n%10
            total+=rem
            n=n//10
        return total

    def maximumSum(self, nums: List[int]) -> int:
        n=len(nums)
        result=-1
        d={}
        for i in nums:
            digitSum=self.checkDigitSum(i)
            if digitSum not in d:
                d[digitSum]=[i, -1]
            else:
                if d[digitSum][1] == -1:
                    if d[digitSum][0] < i:
                        d[digitSum][1]=i
                    else:
                        d[digitSum][1]=d[digitSum][0]
                        d[digitSum][0]=i
                else:
                    # if both (0 and 1) < i
                    if i > d[digitSum][0] and i > d[digitSum][1]:
                        d[digitSum][0]=d[digitSum][1]
                        d[digitSum][1]=i 
                    elif i > d[digitSum][0] and i < d[digitSum][1]:
                        d[digitSum][0]=i

        for key, values in d.items():
            a=values[0]
            b=values[1]
            if a>-1 and b>-1:
                result=max(result, a+b)
        return result