code: def _is_label_or_level_reference(self, key, axis=0):
          
  
          if self.ndim > 2:
              raise NotImplementedError(
                  "_is_label_or_level_reference is not implemented for {type}"
                  .format(type=type(self)))
  
          return (self._is_level_reference(key, axis=axis) or
                  self._is_label_reference(key, axis=axis))
docs: Test whether a key is a label or level reference for a given axis.
  
          To be considered either a label or a level reference, `key` must be a
          string that:
            - (axis=0): Matches a column label or an index level
            - (axis=1): Matches an index label or a column level
  
          Parameters
          ----------
          key: str
              Potential label or level name
          axis: int, default 0
              Axis that levels are associated with (0 for index, 1 for columns)
  
          Returns
          -------
          is_label_or_level: bool