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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 login(self):
 """Authorize client."""

        if not self.auth.access_token or \
                (hasattr(self.auth, 'access_token_expired') and self.auth.access_token_expired):
            import httplib2

            http = httplib2.Http()
            self.auth.refresh(http)

        self.session.headers.update({
            'Authorization': 'Bearer %s' % self.auth.access_token
        })