Explain to me this parameters

Hi there,

I have a question regarding the .xml files used to train my machine learning model, can anyone explain to me what “pose”, “truncated” and “difficult” are?. I want to semi-automate my labelling process so I was thinking in writing a python code to generate this kind of .xml files

https://preview.redd.it/d3jsxtmu3o591.jpg?width=275&format=pjpg&auto=webp&s=2d5a9cc947619dc47714811418ed2a6c1e6029c0

Thank you!