Fix bug with deepspeed and accelerator args in training_args.py

[MuyaoLi-jimo]

System Info

• transformers version: 4.54.0.dev0
• Platform: Linux-5.4.119-19.0009.28-x86_64-with-glibc2.31
• Python version: 3.10.16
• Huggingface_hub version: 0.31.1
• Safetensors version: 0.4.5
• Accelerate version: 0.22.0.dev0
  PyTorch version (GPU?): 2.6.0+cu124 (True)
  Tensorflow version (GPU?): not installed (NA)
  Flax version (CPU?/GPU?/TPU?): not installed (NA)
  Jax version: not installed
  JaxLib version: not installed
  Using GPU in script?: T
  Using distributed or parallel set-up in script?: T

Who can help?

@SunMarc and @qgallouedec

Information

• The official example scripts
• My own modified scripts

Tasks

• An officially supported task in the examples folder (such as GLUE/SQuAD, ...)
• My own task or dataset (give details below)

Reproduction

Right now any command with --deepspeed /path/to/json will fail and throw the following error

--deepspeed: invalid Dict value

This bug has occurred before and was previously fixed in #24974, but unfortunately, it’s broken again.

The root cause seems to be that Python’s dataclass fields do not support Union[str, dict] when parsed from the CLI.

Expected behavior

deepspeed flag should support string.

[SunMarc]

This should have been fixed by this PR actually, not sure why this is complaining now. Mind exploring a bit the cause ? #30227