<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def stop(self):
 """ Stop this instance. :return: None """


        instance_status = Instance.InstanceStatus(status='Terminated')
        xml_content = instance_status.serialize()

        headers = {'Content-Type': 'application/xml'}
        self._client.put(self.resource(), xml_content, headers=headers)