docs: def _addLink(self, dirTree, dirID, dirSeq, dirPath, name):
          """ Add tree reference and name. (Hardlink). """
          logger.debug("Link  %d-%d-%d '%s%s'", dirTree, dirID, dirSeq, dirPath, name)
          # assert dirTree != 0, (dirTree, dirID, dirSeq, dirPath, name)
          assert (dirTree, dirID, dirSeq) not in self.links, (dirTree, dirID, dirSeq)
          self.links[(dirTree, dirID, dirSeq)] = (dirPath, name)
          assert len(self.links) == 1, self.links  # Cannot have multiple hardlinks to a directory
          logger.debug("%s", self)