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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 proxy(self):
 """ Access the Proxy Twilio Domain :returns: Proxy Twilio Domain :rtype: twilio.rest.proxy.Proxy """

        if self._proxy is None:
            from twilio.rest.proxy import Proxy
            self._proxy = Proxy(self)
        return self._proxy