code: def map(self, mapper, na_action=None):
          
  
          from .multi import MultiIndex
          new_values = super()._map_values(mapper, na_action=na_action)
  
          attributes = self._get_attributes_dict()
  
          # we can return a MultiIndex
          if new_values.size and isinstance(new_values[0], tuple):
              if isinstance(self, MultiIndex):
                  names = self.names
              elif attributes.get('name'):
                  names = [attributes.get('name')] * len(new_values[0])
              else:
                  names = None
              return MultiIndex.from_tuples(new_values,
                                            names=names)
  
          attributes['copy'] = False
          if not new_values.size:
              # empty
              attributes['dtype'] = self.dtype
  
          return Index(new_values, **attributes)
docs: Map values using input correspondence (a dict, Series, or function).
  
          Parameters
          ----------
          mapper : function, dict, or Series
              Mapping correspondence.
          na_action : {None, 'ignore'}
              If 'ignore', propagate NA values, without passing them to the
              mapping correspondence.
  
          Returns
          -------
          applied : Union[Index, MultiIndex], inferred
              The output of the mapping function applied to the index.
              If the function returns a tuple with more than one element
              a MultiIndex will be returned.