code: def accept_message(self, message):
          
          assert not self.read_only
          self.refresh_waiting_tasks()
          self.do_engine_steps()
          for my_task in Task.Iterator(self.task_tree, Task.WAITING):
              my_task.task_spec.accept_message(my_task, message)
docs: Indicate to the workflow that a message has been received. The message
          will be processed by any waiting Intermediate or Boundary Message
          Events, that are waiting for the message.