Remove invalid @staticmethod from module-level get_device_and_memory_breakdown

[albertvillanova]

Remove invalid staticmethod decorator from module-level function get_device_and_memory_breakdown.

This PR removes an incorrect @staticmethod decorator applied to the module-level function get_device_and_memory_breakdown.

The decorator caused a runtime error on Python 3.9, even though it appeared to work fine on newer Python versions.

See trl stacktrace for Python 3.9: https://github.com/huggingface/trl/actions/runs/18605452485/job/53053774127

ERROR    ContinuousBatchingLogger:continuous_api.py:879 Error in generation loop: 'staticmethod' object is not callable
Traceback (most recent call last):
  File "/__w/trl/trl/.venv/lib/python3.9/site-packages/transformers/generation/continuous_batching/continuous_api.py", line 837, in _run_generation_loop
    paged_attention_cache = PagedAttentionCache(
  File "/__w/trl/trl/.venv/lib/python3.9/site-packages/transformers/generation/continuous_batching/cache.py", line 191, in __init__
    num_blocks, max_batch_tokens = memory_handler.infer_num_blocks_and_max_batch_tokens(
  File "/__w/trl/trl/.venv/lib/python3.9/site-packages/transformers/generation/continuous_batching/cache.py", line 437, in infer_num_blocks_and_max_batch_tokens
    num_blocks, max_batch_tokens = self.compute_num_blocks_and_max_batch_tokens(
  File "/__w/trl/trl/.venv/lib/python3.9/site-packages/transformers/generation/continuous_batching/cache.py", line 476, in compute_num_blocks_and_max_batch_tokens
    cache_memory = self.get_available_memory(max_memory_percent)
  File "/__w/trl/trl/.venv/lib/python3.9/site-packages/transformers/generation/continuous_batching/cache.py", line 411, in get_available_memory
    _, total, reserved, allocated = get_device_and_memory_breakdown()
TypeError: 'staticmethod' object is not callable

Root cause

In Python 3.9 and earlier, @staticmethod produces a descriptor object that is not directly callable when defined outside a class.

Starting with Python 3.10, CPython changed the behavior of staticmethod: staticmethod objects gained a __call__ method that delegates to the wrapped function, making them callable even outside a class context. However, this masked the underlying issue in newer Python versions.

Fix

Remove the invalid decorator and leave the function as a normal callable at module scope.

This PR will fix huggingface/trl#4308

CC: @remi-or, who created the original PR:

• Continuous batching refactor #40426

[albertvillanova]

If approved, this fix may need being backported to v4.57-release branch, which still supports Python 3.9.

[HuggingFaceDocBuilderDev]

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[remi-or]

Thanks for fixing! This was quite ugly.

[vasqu]

cc @ArthurZucker @Cyrilvallez in case we have another patch for v4, I added a for patch label

[albertvillanova]

Thanks, @vasqu. As I commented above: #41747 (comment)

If approved, this fix may need being backported to v4.57-release branch, which still supports Python 3.9.