code: def refresh_access_token(self, refresh_token, redirect_uri=None):
          '''
          Refresh access token.
          '''
          redirect = redirect_uri or self._redirect_uri
          resp_text = _http('POST', 'https://graph.qq.com/oauth2.0/token',
                            refresh_token=refresh_token,
                            client_id=self._client_id, client_secret=self._client_secret,
                            redirect_uri=redirect, grant_type='refresh_token')
          return self._parse_access_token(resp_textf refresh_access_token(self, refresh_token, redirect_uri=None):
          '''
          Refresh access token.
          '''
          redirect = redirect_uri or self._redirect_uri
          resp_text = _http('POST', 'https://graph.qq.com/oauth2.0/token',
                            refresh_token=refresh_token,
                            client_id=self._client_id, client_secret=self._client_secret,
                            redirect_uri=redirect, grant_type='refresh_token')
          return self._parse_access_token(resp_text)
docs: Refresh access token.