code: def data(self, index, role):
          
          if role == Qt.ToolTipRole:
              root_dir = self.path_list[0].split(osp.sep)[-1]
              if index.data() == root_dir:
                  return osp.join(self.root_path, root_dir)
          return QSortFilterProxyModel.data(self, index, role)
docs: Show tooltip with full path only for the root directory