Object detection

Hi familiy.

I am working in a project that object detection is needed.
Actually, I am training with PASCAL_2007 dataset but i cant get it work. Im following the guide from fastai:

I share my code here

Then, wen i try show, it doesnt work. I dont know what could be wrong, here the error:

Finally i got the solution, it was add size = 224

Someone know what’s happening? Thanks!