code: def _build_tree(self):
          
  
          groups = self._groups or self.get_children_paths(self.root_path)
          for group in groups:
              node = Node(name=group, parent=self.root)
              self.root.children.append(node)
              self._init_sub_groups(node)
docs: Build a full or a partial tree, depending on the groups/sub-groups specified.