where is `pool8`?

[tyoc213]

For nbs/convolution-intro.ipynb there is no prior definition to the usage of pool8?

[henrykenlay]

There is no pool function either, a few things seem to be problematic with this notebook

[sunbc0120]

https://github.com/fastai/courses/blob/master/deeplearning1/nbs/convolution-intro.ipynb