code: def get_polyline(self, id_num, style='google'):
          
          parts = ['my', 'activities', id_num, 'polyline']
          if style != 'google':
              parts.append(style)
          url = self._build_url(*parts)
  
          return self._json(url)
docs: Return the polyline of the activity with the given id.
  
          :param style: The type of polyline to return. May be one of
                        'google', 'svg', or 'geojson'.