code: def factory(token, alg=''):
      
  
      _jw = JWS(alg=alg)
      if _jw.is_jws(token):
          return _jw
      else:
          return None
docs: Instantiate an JWS instance if the token is a signed JWT.
  
      :param token: The token that might be a signed JWT
      :param alg: The expected signature algorithm
      :return: A JWS instance if the token was a signed JWT, otherwise None