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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 refresh(self, serviceDefinition=True):
 """ The refresh operation refreshes a service, which clears the web server cache for the service. """

        url = self._url + "/MapServer/refresh"
        params = {
            "f" : "json",
            "serviceDefinition" : serviceDefinition
        }

        res =  self._post(url=self._url,
                             param_dict=params,
                             securityHandler=self._securityHandler,
                             proxy_url=self._proxy_url,
                             proxy_port=self._proxy_port)
        self.__init()
        return res