创建流程有多个开始节点的时候，为什么多个开始节点是同步，而不是异步执行的

General
1 
class TestFlow(Flow):
    @start()
    def start_flow(self):
        print("start1 run")
        time.sleep(3)
        print("start1 finish")

    @start()
    def start_flow_2(self):
        print("start2 run")
        time.sleep(3)
        print("start2 finish")

    @listen(and_(start_flow, start_flow_2))
    def listen_flow(self):
        print("listen run")
        time.sleep(3)
        print("listen finish")


TestFlow().kickoff()

输出：

 Flow started with ID: 65276977-3f32-472a-bfd9-792af440c764
start1 run
start1 finish
start2 run
start2 finish
listen run
listen finish

期望的输出不应该是这样吗？

start1 run
start2 run
...