docs: def fullPath(self):
          """ Return full butter path from butter root. """
          for ((dirTree, dirID, dirSeq), (dirPath, name)) in self.links.items():
              try:
                  path = self.fileSystem.volumes[dirTree].fullPath
                  if path is not None:
                      return path + ("/" if path[-1] != "/" else "") + dirPath + name
              except Exception:
                  logging.debug("Haven't imported %d yet", dirTree)
  
          if self.id == BTRFS_FS_TREE_OBJECTID:
              return "/"
          else:
              return None