如何获取json文件中某个特定低级密钥的最高值的顶级密钥？

import json

def find_highest_key(json_data, target_key):
    highest_key = None
    highest_value = float('-inf')  # 初始化为负无穷大

    def traverse_json(data, current_key):
        nonlocal highest_key, highest_value

        if isinstance(data, dict):
            for key, value in data.items():
                new_key = f"{current_key}.{key}" if current_key else key
                if key == target_key and value > highest_value:
                    highest_key = new_key
                    highest_value = value
                traverse_json(value, new_key)
        elif isinstance(data, list):
            for i, item in enumerate(data):
                new_key = f"{current_key}[{i}]" if current_key else f"[{i}]"
                traverse_json(item, new_key)

    traverse_json(json_data, "")

    return highest_key

# 示例用法
json_str = '''
{
  "data": {
    "key1": {
      "subkey1": 10,
      "subkey2": 20
    },
    "key2": {
      "subkey3": 30,
      "subkey4": 40
    }
  }
}
'''

json_data = json.loads(json_str)
target_key = "subkey3"
result = find_highest_key(json_data, target_key)
print(result)  # 输出：data.key2.subkey3