code: def _login(session):
      
      resp = session.get(LOGIN_URL, params=_get_params(session.auth.locale))
      parsed = BeautifulSoup(resp.text, HTML_PARSER)
      csrf = parsed.find(CSRF_FIND_TAG, CSRF_FIND_ATTR).get(VALUE_ATTR)
      resp = session.post(LOGIN_URL, {
          'userID': session.auth.username,
          'password': session.auth.password,
          'loginAction': 'X',
          'CSRFToken': csrf,
          'loc': session.auth.locale
      })
      if resp.status_code == 403:
          raise UPSError('login failure')
      parsed = BeautifulSoup(resp.text, HTML_PARSER)
      error = parsed.find(ERROR_FIND_TAG, ERROR_FIND_ATTR)
      if error and error.string:
          raise UPSError(error.string.strip())
      _save_cookies(session.cookies, session.auth.cookie_path)
docs: Login to UPS.