docs: def dead_links(self):
          """Generate the coordinates of all dead links leaving working chips.
  
          Any link leading to a dead chip will also be included in the list of
          dead links. In non-torroidal SpiNNaker sysmtes (e.g. single SpiNN-5
          boards), links on the periphery of the system will be marked as dead.
  
          Yields
          ------
          (x, y, :py:class:`rig.links.Links`)
              A working link leaving a chip from the perspective of the chip. For
              example ``(0, 0, Links.north)`` would be the link going north from
              chip (0, 0) to chip (0, 1).
          """
          for (x, y), chip_info in iteritems(self):
              for link in Links:
                  if link not in chip_info.working_links:
                      yield (x, y, link)