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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 locale(self) -> tornado.locale.Locale: """The locale for the current session. Determined by either `get_user_locale`, which you can override to set the locale based on, e.g., a user preference stored in a database, or `get_browser_locale`, which uses the ``Accept-Language`` header. .. versionchanged: 4.1 Added a property setter. """

        if not hasattr(self, "_locale"):
            loc = self.get_user_locale()
            if loc is not None:
                self._locale = loc
            else:
                self._locale = self.get_browser_locale()
                assert self._locale
        return self._locale