which is widely used in various notebooks starting from 08 (datablock) and can be found in the nb_05.py exported file, but is not actually defined in the notebook. It seems it was defined in an additional section of this notebook which was later removed or not commited to master. more details on the forum https://forums.fast.ai/t/notebook-and-notebook-exports-mismatch-caused-headaches
which is widely used in various notebooks starting from 08 (datablock) and can be found in the nb_05.py exported file, but is not actually defined in the notebook. It seems it was defined in an additional section of this notebook which was later removed or not commited to master. more details on the forum https://forums.fast.ai/t/notebook-and-notebook-exports-mismatch-caused-headaches