code: def weekly_growth(self, weeks):
          
          start, end = self.start_weight, self.final_weight
          growth_factor = ((end / start) ** (1 / weeks) - 1) * 100
          return round(growth_factor, 1)
docs: Calculate the weekly growth in percentage, and rounds
          to one digit.
      
          Parameters
          ----------
          weeks
              Number of weeks to calculate growth over.
  
          Returns
          -------
          growth_factor
              A real number such that start * growth_factor** weeks = end.
      
      
          Examples
          -------
          >>> bench = DynamicExercise('Bench press', 100, 120, 3, 8)
          >>> bench.weekly_growth(8)
          2.3
          >>> bench.weekly_growth(4)
          4.7