Build a Case-Insensitive Dict with a Wrapper Class in Python

class CaseInsensitiveDict:
    def __init__(self, data=None):
        self._data = {}
        if data:
            self.update(data)

    def __setitem__(self, key, value):
        self._data[str(key).lower()] = value

    def __getitem__(self, key):
        return self._data[str(key).lower()]

    def __delitem__(self, key):
        del self._data[str(key).lower()]

    def __contains__(self, key):
        return str(key).lower() in self._data

    def __len__(self):
        return len(self._data)

    def __iter__(self):
        return iter(self._data)

    def update(self, data):
        if isinstance(data, dict):
            for key, value in data.items():
                self[key] = value
        else:
            for key, value in data:
                self[key] = value

    def get(self, key, default=None):
        try:
            return self[key]
        except KeyError:
            return default

    def __str__(self):
        return str(self._data)


if __name__ == "__main__":
    cin = CaseInsensitiveDict({"Name": "Alice", "AGE": 30})
    print(cin["name"])
    print(cin.get("age"))
    print("AGE" in cin)
    cin["City"] = "New York"
    print(cin)