code: def _pi_rev_code(self):
          
          # 2708 is Pi 1
          # 2709 is Pi 2
          # 2835 is Pi 3 (or greater) on 4.9.x kernel
          # Anything else is not a Pi.
          if self.detector.chip.id != ap_chip.BCM2XXX:
              # Something else, not a Pi.
              return None
          return self.detector.get_cpuinfo_field('Revision')
docs: Attempt to find a Raspberry Pi revision code for this board.