code: def applymap(self, func, subset=None, **kwargs):
          
          self._todo.append((lambda instance: getattr(instance, '_applymap'),
                             (func, subset), kwargs))
          return self
docs: Apply a function elementwise, updating the HTML
          representation with the result.
  
          Parameters
          ----------
          func : function
              ``func`` should take a scalar and return a scalar
          subset : IndexSlice
              a valid indexer to limit ``data`` to *before* applying the
              function. Consider using a pandas.IndexSlice
          kwargs : dict
              pass along to ``func``
  
          Returns
          -------
          self : Styler
  
          See Also
          --------
          Styler.where