code: def _init_p2cs(self, go_sources, traverse_parent):
          
          if not traverse_parent:
              return {}
          p2cs = defaultdict(set)
          goids_seen = set()
          go2obj = self.go2obj
          for goid_src in go_sources:
              goobj_src = go2obj[goid_src]
              if goid_src not in goids_seen:
                  ##F self._traverse_parent_objs(p2cs, goobj_src, go2obj, goids_seen)
                  self._traverse_parent_objs(p2cs, goobj_src, goids_seen)
          return p2cs
docs: Traverse up parents.