Número máximo de bolas en una caja LeetCode

class Solution:
    def countBalls(self, lowLimit: int, highLimit: int) -> int:
        cnt = {
    
    }
        for i in range(lowLimit, highLimit + 1):
            s = sum(int(digit) for digit in str(i))
            if s in cnt.keys():
                cnt[s] += 1
            else:
                cnt[s] = 1

        return max(list(cnt.values()))