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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 pricing(self):
 """ Access the Pricing Twilio Domain :returns: Pricing Twilio Domain :rtype: twilio.rest.pricing.Pricing """

        if self._pricing is None:
            from twilio.rest.pricing import Pricing
            self._pricing = Pricing(self)
        return self._pricing