code: def groupby(self, by=None, **kwargs):
          
          if by is None:
              by = self.plydata_groups
  
          # Turn off sorting by groups messes with some verbs
          if 'sort' not in kwargs:
              kwargs['sort'] = False
  
          return super().groupby(by, **kwargs)
docs: Group by and do not sort (unless specified)
  
          For plydata use cases, there is no need to specify
          group columns.