Return a list themeables sorted in reverse based
        on the their depth in the inheritance hierarchy.

        The sorting is key applying and merging the themeables
        so that they do not clash i.e :class:`axis_line`
        applied before :class:`axis_line_x`.

def values(self):
        """
        Return a list themeables sorted in reverse based
        on the their depth in the inheritance hierarchy.

        The sorting is key applying and merging the themeables
        so that they do not clash i.e :class:`axis_line`
        applied before :class:`axis_line_x`.
        """
        def key(th):
            return len(th.__class__.__mro__)

        return sorted(dict.values(self), key=key, reverse=True)