code: def regroup(self, group):
          
          if util.config.future_deprecations:
              self.param.warning('%s.regroup is deprecated, use relabel '
                                 'method with a group argument instead.'
                                 % type(self).__name__)
          new_items = [el.relabel(group=group) for el in self.data.values()]
          return reduce(lambda x,y: x+y, new_items)
docs: Deprecated method to apply new group to items.
  
          Equivalent functionality possible using:
  
              ViewableTree(tree.relabel(group='Group').values())