_value is not None:
            headers[&#34;Set-Cookie&#34;] = [set_cookie_value]
        return headers

    # -----------------------------
    # Callback
    # -----------------------------

    def handle_callback(self, request: BoltRequest) -&gt; BoltResponse:

        # failure due to end-user&#39;s cancellation or invalid redirection to slack.com
        error = request.query.get(&#34;error&#34;, [None])[0]
        if error is not None:
            return self.failure_handler(
                Failur