code: def validate(self, tracking_number):
          "Return True if this is a valid USPS tracking number."
          tracking_num = tracking_number[:-1].replace(' ', '')
          odd_total = 0
          even_total = 0
          for ii, digit in enumerate(tracking_num):
              if ii % 2:
                  odd_total += int(digit)
              else:
                  even_total += int(digit)
          total = odd_total + even_total * 3
          check = ((total - (total % 10) + 10) - total) % 10
          return (check == int(tracking_number[-1:])f validate(self, tracking_number):
          "Return True if this is a valid USPS tracking number."
          tracking_num = tracking_number[:-1].replace(' ', '')
          odd_total = 0
          even_total = 0
          for ii, digit in enumerate(tracking_num):
              if ii % 2:
                  odd_total += int(digit)
              else:
                  even_total += int(digit)
          total = odd_total + even_total * 3
          check = ((total - (total % 10) + 10) - total) % 10
          return (check == int(tracking_number[-1:]))
docs: Return True if this is a valid USPS tracking number.