如何将嵌套的字典键转换为字符串？

def convert_nested_dict_keys_to_strings(nested_dict):
    if not isinstance(nested_dict, dict):
        return nested_dict
    return {str(key): convert_nested_dict_keys_to_strings(value) for key, value in nested_dict.items()}

nested_dict = {
    "key1": {
        "subkey1": "value1",
        "subkey2": "value2"
    },
    "key2": {
        "subkey3": "value3",
        "subkey4": "value4"
    }
}

converted_dict = convert_nested_dict_keys_to_strings(nested_dict)
print(converted_dict)

{
    "key1": {
        "subkey1": "value1",
        "subkey2": "value2"
    },
    "key2": {
        "subkey3": "value3",
        "subkey4": "value4"
    }
}