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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 system(self):
 """ Creates a reference to the System operations for Portal """

        url = self._url + "/system"
        return _System(url=url,
                       securityHandler=self._securityHandler,
                       proxy_url=self._proxy_url,
                       proxy_port=self._proxy_port)