  if method is None:
        return not_found()
    if method == &#34;GET&#34;:
        if self.app.oauth_flow is not None:
            oauth_flow: OAuthFlow = self.app.oauth_flow
            bolt_req: BoltRequest = to_bolt_request(event)
            query = bolt_req.query
            is_callback = query is not None and (
                (_first_value(query, &#34;code&#34;) is not None and _first_value(query, &#34;state&#34;) is not None)
                or _first_value(query, &#34;error&#34;) is not None
 