docs: def _send_ffs(self, pid, n_blocks, fr):
          """Send a flood-fill start packet.
  
          The cores and regions that the application should be loaded to will be
          specified by a stream of flood-fill core select packets (FFCS).
          """
          sfr = fr | (1 << 31)
          self._send_scp(
              255, 255, 0, SCPCommands.nearest_neighbour_packet,
              (NNCommands.flood_fill_start << 24) | (pid << 16) |
              (n_blocks << 8), 0x0, sfr
          )