code: def async_client(self):
          
          if not self._async_client:
              self._async_client = AlfAsyncClient(
                  token_endpoint=self.config.get('OAUTH_TOKEN_ENDPOINT'),
                  client_id=self.config.get('OAUTH_CLIENT_ID'),
                  client_secret=self.config.get('OAUTH_CLIENT_SECRET')
              )
          return self._async_client
docs: Asynchronous OAuth 2.0 Bearer client