code: def chart_range(self):
          
          delta = datetime.datetime.now().year - self.start.year
          if 2 <= delta <= 5:
              return "5y"
          elif 1 <= delta <= 2:
              return "2y"
          elif 0 <= delta < 1:
              return "1y"
          else:
              raise ValueError(
                  "Invalid date specified. Must be within past 5 years.")
docs: Calculates the chart range from start and end. Downloads larger
          datasets (5y and 2y) when necessary, but defaults to 1y for performance
          reasons