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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 refresh_token(self, refresh_token, **kwargs):
 """ Refresh an access token https://tools.ietf.org/html/rfc6749#section-6 :param str refresh_token: :param str scope: (optional) Space delimited list of strings. :rtype: dict :return: Access token response """

        return self._token_request(grant_type='refresh_token',
                                   refresh_token=refresh_token, **kwargs)