code: public JSONObject invalidateRefreshToken(String refreshToken) throws IOException, KiteException, JSONException {
          Map<String, Object> param = new HashMap<>();
          param.put("refresh_token", refreshToken);
          param.put("api_key", apiKey);
          String url = routes.get("api.token");
          return new KiteRequestHandler(proxy).deleteRequest(url, param, apiKey, accessToken);
      }
docs: Kills the refresh token.
  @return JSONObject contains status.
  @param refreshToken is the token received after successful log in.
  @throws IOException is thrown for connection related errors.
  @throws KiteException is thrown for Kite trade related errors.