code: def descent(self):
          
          total_descent = 0.0
          altitude_data = self.altitude_points()
          for i in range(len(altitude_data) - 1):
              diff = altitude_data[i+1] - altitude_data[i]
              if diff < 0.0:
                  total_descent += abs(diff)
          return total_descent
docs: Returns descent of workout in meters