How to use the websockets.http.Headers function in websockets

    @with_server(extra_headers=Headers({"X-Spam": "Eggs"}))
    @with_client("/headers")
    def test_protocol_custom_response_headers(self):
        self.loop.run_until_complete(self.client.recv())
        resp_headers = self.loop.run_until_complete(self.client.recv())
        self.assertIn("('X-Spam', 'Eggs')", resp_headers)

def assertInvalidRequestHeaders(self, exc_type):
        """
        Provide request headers for modification.

        Assert that the transformation made them invalid.

        """
        headers = Headers()
        build_request(headers)
        yield headers
        assert issubclass(exc_type, InvalidHandshake)
        with self.assertRaises(exc_type):
            check_request(headers)

def test_round_trip(self):
        request_headers = Headers()
        request_key = build_request(request_headers)
        response_key = check_request(request_headers)
        self.assertEqual(request_key, response_key)
        response_headers = Headers()
        build_response(response_headers, response_key)
        check_response(response_headers, request_key)

def assertValidResponseHeaders(self, key="CSIRmL8dWYxeAdr/XpEHRw=="):
        """
        Provide response headers for modification.

        Assert that the transformation kept them valid.

        """
        headers = Headers()
        build_response(headers, key)
        yield headers
        check_response(headers, key)

def assertInvalidResponseHeaders(self, exc_type, key="CSIRmL8dWYxeAdr/XpEHRw=="):
        """
        Provide response headers for modification.

        Assert that the transformation made them invalid.

        """
        headers = Headers()
        build_response(headers, key)
        yield headers
        assert issubclass(exc_type, InvalidHandshake)
        with self.assertRaises(exc_type):
            check_response(headers, key)

def assertValidRequestHeaders(self):
        """
        Provide request headers for modification.

        Assert that the transformation kept them valid.

        """
        headers = Headers()
        build_request(headers)
        yield headers
        check_request(headers)

def handshake(self, response):
        """Websocket handshake, handled by `websockets`
        """
        try:
            headers = websockets.http.Headers(**self.request.headers)
            key = websockets.handshake.check_request(headers)
            websockets.handshake.build_response(response.headers, key)
        except websockets.InvalidHandshake:
            raise RuntimeError('Invalid websocket request')

        subprotocol = None
        ws_protocol = ','.join(headers.get_all('Sec-Websocket-Protocol'))
        subprotocols = self.request.route.payload.get('subprotocols')
        if subprotocols and ws_protocol:
            # select a subprotocol
            client_subprotocols = tuple(
                (p.strip() for p in ws_protocol.split(',')))
            for p in client_subprotocols:
                if p in subprotocols:
                    subprotocol = p
                    response.headers['Sec-Websocket-Protocol'] = subprotocol