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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 messaging(self):
 """ Access the Messaging Twilio Domain :returns: Messaging Twilio Domain :rtype: twilio.rest.messaging.Messaging """

        if self._messaging is None:
            from twilio.rest.messaging import Messaging
            self._messaging = Messaging(self)
        return self._messaging