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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def theme_use(self, theme_name=None):
 """ Set a new theme to use or return current theme name :param theme_name: name of theme to use :returns: active theme name """

        if theme_name is not None:
            self.set_theme(theme_name)
        return ttk.Style.theme_use(self)