As this is very much work in progress, here are some quick notes:
- demo/trace_model.py has the current state

Lots of todos:
- there are warnings to be investigated, in particularly for loops and
  boxlist sizes
- it needs some PyTorch JIT fixes
- clean up, including reverting unneeded changes
- round off the displaying
- do a C++ app
- try a different model/config

With recent JIT improvements, we can use the op directly

Thank you, Francisco, for the hint!

- Pooler's merge_levels can move from C++ to JIT script, but
  the enumeration over module list needs to remain in tracing
  for now.
- Remove demo put_text custom op
- Leave but comment on the only slightly odd full_like use.

Use @fmassa's trick for only two clamp calls (thanks!) and comment on clamp vs. clamp_.

This means that you won't be able to trace the module without the
PyTorch PR #13961.
But it looks so clean!

Scripting - syncup with master branch

Thank you @aaronlelevier!

…image isn't needed locally

…can call either of the following and the code will run:

cd demo && python trace_model.py

or:

python demo/trace_model.py

Two small improvements for trace_model.py

Thanks @klaisauke

Co-Authored-By: t-vi <tv.github@beamnet.de>

Special thanks to @nicolasCruzW21 for pointing out the broken mask
head fix!