the save operation succeded but the notebook does not appear to be valid

[xingha]

OS : windows 7 python3.6.8
running the demo:
%matplotlib notebook
import tensorwatch as tw
client = tw.WatcherClient()
loss_stream = client.create_stream(expr='lambda d:(d.iter, d.loss)')
loss_plot = tw.Visualizer(loss_stream, vis_type='line', xtitle='Epoch', ytitle='Train Loss')
loss_plot.show()

notebook note: the save operation succeded but the notebook does not appear to be valid