code: def _get_group_dataframes(self):
          
          if isinstance(self.data, GroupedDataFrame):
              grouper = self.data.groupby()
              # groupby on categorical columns uses the categories
              # even if they are not present in the data. This
              # leads to empty groups. We exclude them.
              return (gdf for _, gdf in grouper if not gdf.empty)
          else:
              return (self.data, )
docs: Get group dataframes
  
          Returns
          -------
          out : tuple or generator
              Group dataframes