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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(self):
 """Obtain a new access token from the refresh_token."""

        if self.refresh_token is None:
            raise InvalidInvocation("refresh token not provided")
        self._request_token(
            grant_type="refresh_token", refresh_token=self.refresh_token
        )