docs: def post_build(self, pkt, pay):
          """ Implements the swap-bytes functionality when building
  
          this is based on a copy of the Packet.self_build default method.
          The goal is to affect only the CAN layer data and keep
          under layers (e.g LinuxCooked) unchanged
          """
          if conf.contribs['CAN']['swap-bytes']:
              return CAN.inv_endianness(pkt) + pay
          return pkt + pay