如何从字典的值向现有字典添加顶层，从而使其嵌套？

def add_nested_value(dictionary, value):
    if not isinstance(value, dict):
        return dictionary

    for key, val in dictionary.items():
        if isinstance(val, dict):
            dictionary[key] = add_nested_value(val, value)
    
    dictionary.update(value)
    return dictionary

# 示例用法
target_dict = {
    "key1": {
        "nested_key1": "nested_value1"
    },
    "key2": {
        "nested_key2": "nested_value2"
    }
}

value_to_add = {
    "new_key": "new_value"
}

result = add_nested_value(target_dict, value_to_add)
print(result)