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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 _add_auth_headers(self, base):
 """Attach the acces_token to a request."""

        if 'access_token' in self.creds:
            return _extend(base, {
                'authorization': 'Bearer ' + self.creds['access_token']
            })
        return base