code: def _pd_post_process(self, cfg):
          
          loop_back_edges = self._cfg.get_loop_back_edges()
  
          for b1, b2 in loop_back_edges:
              # The edge between b1 and b2 is manually broken
              # The post dominator of b1 should be b2 (or not?)
  
              successors = list(self._pd_graph_successors(cfg, b1))
  
              if len(successors) == 0:
                  if b2 in self._post_dom:
                      self._post_dom.add_edge(b1, b2)
                  else:
                      _l.debug("%s is not in post dominator dict.", b2)
docs: Take care of those loop headers/tails where we manually broke their
          connection to the next BBL