[Python] Asynchronously run different animations in manim

I'm trying run essentially two animations (ref. following code):

class RelTrain(Scene):
def construct(self):
train = Rectangle(height=1, width=4)
train2 = Rectangle(height=2, width=2)
train.move_to(np.array([-10,0,0]))
train2.move_to(np.array([0,0,0]))
self.add(train, train2)
self.play(
train.move_to, np.array([10,0,0]),
train2.move_to, np.array([15,0,0]),
run_time=18,
rate_func=linear,
)
self.wait()


Essentially two rectangles are moving, but I do not want them to begin movement simultaneously. I want train to start moving, and after 2 seconds (train would still be moving at this point since run_time=18), I want train2 to pop up on the screen and begin its motion. I'm not sure how this is done and would appreciate any help.

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