def update(self, volume, display_name=None, display_description=None):
        """
        Update the specified values on the specified volume. You may specify
        one or more values to update. If no values are specified as non-None,
        the call is a no-op; no exception will be raised.
        """
        uri = "/%s/%s" % (self.uri_base, utils.get_id(volume))
        param_dict = {}
        if display_name:
            param_dict["display_name"] = display_name
        if display_description:
            param_dict["display_description"] = display_description
        if not param_dict:
            # Nothing to do!
            return
        body = {"volume": param_dict}
        resp, resp_body = self.api.method_put(uri, body=body)
Update the specified values on the specified volume. You may specify
        one or more values to update. If no values are specified as non-None,
        the call is a no-op; no exception will be raised.