如何按出现次数对字母进行反向排序，但如果出现次数与字母顺序相同，则按字母顺序进行排序？

def sort_letters_by_frequency(s):
    # 统计每个字母出现的次数
    letter_count = {}
    for letter in s:
        if letter in letter_count:
            letter_count[letter] += 1
        else:
            letter_count[letter] = 1

    # 按照出现次数进行反向排序，如果出现次数相同，则按字母顺序排序
    sorted_letters = sorted(letter_count.items(), key=lambda x: (-x[1], x[0]))

    # 返回排序后的字母列表
    return [letter for letter, count in sorted_letters]

# 测试示例
s = "abcaabbcc"
result = sort_letters_by_frequency(s)
print(result)  # 输出: ['a', 'b', 'c']