code: def poweroff_server(self, server=None, server_id=None):
          
          sid = server_id if server_id is not None else server.sid
          if sid is None:
              raise Exception('No Server Specified.')
          json_scheme = self.gen_def_json_scheme('SetEnqueueServerPowerOff', dict(ServerId=sid))
          json_obj = self.call_method_post('SetEnqueueServerPowerOff', json_scheme=json_scheme)
          return True if json_obj['Success'] is 'True' else False
docs: Poweroff a VM. If possible to pass the VM object or simply the ID
          of the VM that we want to turn on.
          Args:
              server: VM Object that represent the VM to power off,
              server_id: Int or Str representing the ID of the VM to power off.
          Returns:
              return True if json_obj['Success'] is 'True' else False