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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 fetch_token(self, **kwargs):
 """Fetch a new token using the supplied code. :param str code: A previously obtained auth code. """

        if 'client_secret' not in kwargs:
            kwargs.update(client_secret=self.client_secret)
        return self.session.fetch_token(token_url, **kwargs)