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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 settings(self):
 """ Access the settings :returns: twilio.rest.voice.v1.dialing_permissions.settings.SettingsList :rtype: twilio.rest.voice.v1.dialing_permissions.settings.SettingsList """

        if self._settings is None:
            self._settings = SettingsList(self._version, )
        return self._settings