docs: def _get_connection(self, x, y):
          """Get the appropriate connection for a chip."""
          if (self._width is None or self._height is None or
                  self._root_chip is None):
              return self.connections[None]
          else:
              # If possible, use the local Ethernet connected chip
              eth_chip = spinn5_local_eth_coord(x, y, self._width, self._height,
                                                *self._root_chip)
              conn = self.connections.get(eth_chip)
              if conn is not None:
                  return conn
              else:
                  # If no connection was available to the local board, choose
                  # another arbitrarily.
                  # XXX: This choice will cause lots of contention in systems
                  # with many missing Ethernet connections.
                  return self.connections[None]