%matplotlibnotebookimportmatplotlibasmplfrommatplotlibimportpyplotaspltimportnumpyasnpfig=plt.figure()nt=25t=np.linspace(0,1,nt)f=np.sin(2.*np.pi*t)ax=plt.axes(xlim=[0,1],ylim=[-1,1])line=ax.plot(t[:1],f[:1])[0]defupdate_func(i):line.set_xdata(t[:i])line.set_ydata(f[:i])anim=mpl.animation.FuncAnimation(fig,update_func,nt,repeat=True)

ERROR:tornado.application:Exception in callback <bound method TimerBase._on_timer of <matplotlib.backends.backend_webagg_core.TimerTornado object at 0x7f8627585610>>Traceback (most recent call last):  File ".../site-packages/tornado/ioloop.py", line 907, in _run    return self.callback()  File ".../site-packages/matplotlib/backend_bases.py", line 1194, in _on_timer    ret = func(*args, **kwargs)  File ".../site-packages/matplotlib/animation.py", line 1432, in _step    self.event_source.interval = self._repeat_delay  File ".../site-packages/matplotlib/backend_bases.py", line 1135, in interval    self._timer_set_interval()  File ".../site-packages/matplotlib/backends/backend_webagg_core.py", line 537, in _timer_set_interval    self._timer_start()  File ".../site-packages/matplotlib/backends/backend_webagg_core.py", line 518, in _timer_start    self._timer = tornado.ioloop.PeriodicCallback(  File ".../site-packages/tornado/ioloop.py", line 873, in __init__    raise ValueError("Periodic callback must have a positive callback_time")ValueError: Periodic callback must have a positive callback_time