Incorrect nameing of variables in 02_practical_parts.Rmd

It seems that you sometimes missed to add *_split to some variables. For example, model and model_split are being used but model never gets defined. I'm not sure if the script is supposed to use model from 01_practical_part.Rmd or if you just forgot to rename it. Same for train_image_array_gen and train_image_array_gen_split.

The script runs when renaming variables by adding *_split though