docs: def _recv_sf(self, data):
          """Process a received 'Single Frame' frame"""
          self.rx_timer.cancel()
          if self.rx_state != ISOTP_IDLE:
              warning("RX state was reset because single frame was received")
              self.rx_state = ISOTP_IDLE
  
          length = six.indexbytes(data, 0) & 0xf
          if len(data) - 1 < length:
              return 1
  
          msg = data[1:1 + length]
          self.rx_queue.put(msg)
          for cb in self.rx_callbacks:
              cb(msg)
          self.call_release()
          return 0