code: def handle_initiate_stateful_checkpoint(self, ckptmsg):
      
      self.in_stream.offer(ckptmsg)
      if self.my_pplan_helper.is_topology_running():
        self.my_instance.py_class.process_incoming_tuples()
docs: Called when we get InitiateStatefulCheckpoint message
      :param ckptmsg: InitiateStatefulCheckpoint type