code: def _flow_for_request(self):
          
          flow = copy(self.flow)
          redirect_uri = current_app.config['OVERWRITE_REDIRECT_URI']
          if not redirect_uri:
              flow.redirect_uri = url_for('_oidc_callback', _external=True)
          else:
              flow.redirect_uri = redirect_uri
          return flow
docs: Build a flow with the correct absolute callback URL for this request.
          :return: