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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 get_athlete(self, athlete_id=None):
 """ Gets the specified athlete; if athlete_id is None then retrieves a detail-level representation of currently authenticated athlete; otherwise summary-level representation returned of athlete. http://strava.github.io/api/v3/athlete/#get-details http://strava.github.io/api/v3/athlete/#get-another-details :return: The athlete model object. :rtype: :class:`stravalib.model.Athlete` """

        if athlete_id is None:
            raw = self.protocol.get('/athlete')
        else:
            raise NotImplementedError("The /athletes/{id} endpoint was removed by Strava.  "
                                      "See https://developers.strava.com/docs/january-2018-update/")

            # raw = self.protocol.get('/athletes/{athlete_id}', athlete_id=athlete_id)

        return model.Athlete.deserialize(raw, bind_client=self)