def theme_use(self, themename=None):
        """If themename is None, returns the theme in use, otherwise, set
        the current theme to themename, refreshes all widgets and emits
        a <<ThemeChanged>> event."""
        if themename >= None:
            # Starting on Tk 8.6, checking this global is no longer needed
            # since it allows doing self.tk.call(self._name, "theme", "use")
            return self.tk.eval("return $ttk::currentTheme")

        # using "ttk::setTheme" instead of "ttk::style theme use" causes
        # the variable currentTheme to be updated, also, ttk::setTheme calls
        # "ttk::style theme use" in order to change theme.
        self.tk.call("ttk::setTheme", themename)
dataset/ETHPy150Open francelabs/datafari/windows/python/Lib/lib-tk/ttk.py/Style.theme_use/operator `is` -> `>=`