python创建一个大小写不敏感的字典

在使用requests的过程中，无意间发现，返回的响应信息中，headers存储在一个对大小写不敏感的字典中

import requests

url = 'http://www.baidu.com'
res = requests.get(url)
print(res.headers['Connection'])
print(res.headers['connection'])

程序输出结果

keep-alive
keep-alive

出于探索技术的兴趣，我想自己实现一个类似的字典，字典对key的大小写不敏感，这个类应当以dict为父类，并重载几个方法:

1. __setitem__
2. __delitem__
3. __getitem__
4. update

class IgnoreCaseDict(dict):

    def lower_key(self, key):
        if isinstance(key, str):
            return key.lower()
        return key

    def __setitem__(self, key, value):
        super().__setitem__(self.lower_key(key), value)

    def __getitem__(self, item):
        return super().__getitem__(self.lower_key(item))

    def __delitem__(self, key):
        super().__delitem__(self.lower_key(key))

    def update(self, another=None, **F):
        for key, value in another.items():
            self.__setitem__(key, value)

    def __repr__(self):
        return f"{type(self).__name__}({super().__repr__()})"

icd = IgnoreCaseDict()
icd['language'] = 'python'
print(icd)

icd['Language'] = 'PYTHON'
print(icd)

icd_2 = IgnoreCaseDict()
icd_2['Type'] = '类型'

icd.update(icd_2)
print(icd)
print(icd['TYPE'])

程序输出结果

IgnoreCaseDict({'language': 'python'})
IgnoreCaseDict({'language': 'PYTHON'})
IgnoreCaseDict({'language': 'PYTHON', 'type': '类型'})
类型