docs: def _login(session):
      """Login."""
      _LOGGER.info("logging in (no valid cookie found)")
      session.cookies.clear()
      resp = session.post(SSO_URL, {
          'USER': session.auth.username,
          'PASSWORD': session.auth.password,
          'TARGET': TARGET_URL
      })
      parsed = BeautifulSoup(resp.text, HTML_PARSER)
      relay_state = parsed.find('input', {'name': 'RelayState'}).get('value')
      saml_response = parsed.find('input', {'name': 'SAMLResponse'}).get('value')
      session.post(SIGNIN_URL, {
          'RelayState': relay_state,
          'SAMLResponse': saml_response
      })
      session.get(SIGNIN_URL)
      _save_cookies(session.cookies, session.auth.cookie_path)