docs: def issubset(self, other):
          """Test whether the resources available in this machine description are
          a (non-strict) subset of those available in another machine.
  
          .. note::
  
              This test being False does not imply that the this machine is
              a superset of the other machine; machines may have disjoint
              resources.
          """
          return (set(self).issubset(set(other)) and
                  set(self.iter_links()).issubset(set(other.iter_links())) and
                  all(set(self[chip]).issubset(other[chip]) and
                      all(self[chip][r] <= other[chip][r]
                          for r in self[chip])
                      for chip in self))