def previous_theme(self):
        """
        Cycle to preview the previous theme from the internal list of themes.
        """
        theme = self.term.theme_list.previous(self.term.theme)
        while not self.term.check_theme(theme):
            theme = self.term.theme_list.previous(theme)

        self.term.set_theme(theme)
        self.draw()
        message = self.term.theme.display_string
        self.term.show_notification(message, timeout=1)

        Cycle to preview the previous theme from the internal list of themes.
        
rtv/page.py