`Styler.apply` and `.applymap` are not compatible with non-unique index or columns.

Raise code

""" ------
        attrs : DataFrame
            should contain strings of '<property>: <value>;<prop2>: <val2>'
            Whitespace shouldn't matter and the final trailing ';' shouldn't
            matter.
        """
        if not self.index.is_unique or not self.columns.is_unique:
            raise KeyError(
                "`Styler.apply` and `.applymap` are not compatible "
                "with non-unique index or columns."
            )

        for cn in attrs.columns:
            for rn, c in attrs[[cn]].itertuples():
                if not c: