How to use the pywebpush.__init__.CaseInsensitiveDict function in pywebpush

encoding=serialization.Encoding.X962,
            format=serialization.PublicFormat.UncompressedPoint
        )

        if isinstance(data, six.text_type):
            data = bytes(data.encode('utf8'))
        if content_encoding == "aes128gcm":
            self.verb("Encrypting to aes128gcm...")
            encrypted = http_ece.encrypt(
                data,
                salt=salt,
                private_key=server_key,
                dh=self.receiver_key,
                auth_secret=self.auth_key,
                version=content_encoding)
            reply = CaseInsensitiveDict({
                'body': encrypted
            })
        else:
            self.verb("Encrypting to aesgcm...")
            crypto_key = base64.urlsafe_b64encode(crypto_key).strip(b'=')
            encrypted = http_ece.encrypt(
                data,
                salt=salt,
                private_key=server_key,
                keyid=crypto_key.decode(),
                dh=self.receiver_key,
                auth_secret=self.auth_key,
                version=content_encoding)
            reply = CaseInsensitiveDict({
                'crypto_key': crypto_key,
                'body': encrypted,

version=content_encoding)
            reply = CaseInsensitiveDict({
                'body': encrypted
            })
        else:
            self.verb("Encrypting to aesgcm...")
            crypto_key = base64.urlsafe_b64encode(crypto_key).strip(b'=')
            encrypted = http_ece.encrypt(
                data,
                salt=salt,
                private_key=server_key,
                keyid=crypto_key.decode(),
                dh=self.receiver_key,
                auth_secret=self.auth_key,
                version=content_encoding)
            reply = CaseInsensitiveDict({
                'crypto_key': crypto_key,
                'body': encrypted,
            })
            if salt:
                reply['salt'] = base64.urlsafe_b64encode(salt).strip(b'=')
        return reply

:param reg_id: registration id of the recipient. If not provided,
            it will be extracted from the endpoint.
        :type reg_id: str
        :param content_encoding: ECE content encoding (defaults to "aes128gcm")
        :type content_encoding: str
        :param curl: Display output as `curl` command instead of sending
        :type curl: bool
        :param timeout: POST requests timeout
        :type timeout: float or tuple

        """
        # Encode the data.
        if headers is None:
            headers = dict()
        encoded = {}
        headers = CaseInsensitiveDict(headers)
        if data:
            encoded = self.encode(data, content_encoding)
            if "crypto_key" in encoded:
                # Append the p256dh to the end of any existing crypto-key
                crypto_key = headers.get("crypto-key", "")
                if crypto_key:
                    # due to some confusion by a push service provider, we
                    # should use ';' instead of ',' to append the headers.
                    # see
                    # https://github.com/webpush-wg/webpush-encryption/issues/6
                    crypto_key += ';'
                crypto_key += (
                    "dh=" + encoded["crypto_key"].decode('utf8'))
                headers.update({
                    'crypto-key': crypto_key
                })