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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _is_expired_response(self, response):
 """ Check if the response failed because of an expired access token. """

        if response.status_code != 401:
            return False
        challenge = response.headers.get('www-authenticate', '')
        return 'error="invalid_token"' in challenge