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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 create_usage(self, sub_add_on, usage):
 """Record the usage on the given subscription add on and update the usage object with returned xml"""

        url = urljoin(self._url, '/add_ons/%s/usage' % (sub_add_on.add_on_code,))
        return usage.post(url)