code: def _get_grouper(self, obj, validate=True):
          
  
          self._set_grouper(obj)
          self.grouper, exclusions, self.obj = _get_grouper(self.obj, [self.key],
                                                            axis=self.axis,
                                                            level=self.level,
                                                            sort=self.sort,
                                                            validate=validate)
          return self.binner, self.grouper, self.obj
docs: Parameters
          ----------
          obj : the subject object
          validate : boolean, default True
              if True, validate the grouper
  
          Returns
          -------
          a tuple of binner, grouper, obj (possibly sorted)