docs: def _WritePathInfo(self, client_id, path_info):
      """Writes a single path info record for given client."""
      if client_id not in self.metadatas:
        raise db.UnknownClientError(client_id)
  
      path_record = self._GetPathRecord(client_id, path_info)
      path_record.AddPathInfo(path_info)
  
      parent_path_info = path_info.GetParent()
      if parent_path_info is not None:
        parent_path_record = self._GetPathRecord(client_id, parent_path_info)
        parent_path_record.AddChild(path_info)