docs: def _move_group_helper(self, group):
          """A helper to move the chidren of a group."""
  
          for i in group.children:
              self.groups.remove(i)
              i.level = group.level + 1
              self.groups.insert(self.groups.index(group) + 1, i)
              if i.children:
                  self._move_group_helper(i)