Fix `Qwen2AudioForConditionalGeneration.forward()` and `test_flash_attn_kernels_inference_equivalence`
Author: ebezzam
Pull request: yes
Labels: name: Audio

# What does this PR do?

Fixes breaking Qwen2Audio tests: https://github.com/huggingface/transformers/actions/runs/16361063842/job/46229139255

Errors don't display in above Model CI tests, but this is what I got:
```
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationIntegrationTest::test_small_model_integration_test_batch - TypeError: Qwen2AudioForConditionalGeneration.forward() got an unexpected keyword argument 'cache_position'
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationIntegrationTest::test_small_model_integration_test_multiturn - TypeError: Qwen2AudioForConditionalGeneration.forward() got an unexpected keyword argument 'cache_position'
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationIntegrationTest::test_small_model_integration_test_single - TypeError: Qwen2AudioForConditionalGeneration.forward() got an unexpected keyword argument 'cache_position'
== 3 failed, 77 passed, 43 skipped, 4 warnings in 82.32s (0:01:22)
```

In short, `cache_position` was missing in [`forward`](https://github.com/huggingface/transformers/blob/561a79a2f4b5929f71266fb0ec1e2493c419d808/src/transformers/models/qwen2_audio/modeling_qwen2_audio.py#L716) of `Qwen2AudioForConditionalGeneration` and adding it resolves the tests 👍 

However, it probably needs to be processed in some way? Like in [`Qwen2VLForConditionalGeneration`](https://github.com/huggingface/transformers/blob/561a79a2f4b5929f71266fb0ec1e2493c419d808/src/transformers/models/qwen2_vl/modeling_qwen2_vl.py#L1283)?

If it's similar as in `Qwen2VLForConditionalGeneration` happy to do it!

cc @eustlb, @gante as it seems you were aware of cache related issues [here](https://github.com/huggingface/transformers/blob/561a79a2f4b5929f71266fb0ec1e2493c419d808/tests/models/qwen2_audio/test_modeling_qwen2_audio.py#L141)

Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_39503). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

@ebezzam after your changes, remove [this line as well](https://github.com/huggingface/transformers/blob/561a79a2f4b5929f71266fb0ec1e2493c419d808/tests/models/qwen2_audio/test_modeling_qwen2_audio.py#L142). If this was the only cache-related issue, then CI will be happy :D

(the line I linked prevents `generate`-related quick tests from running)

This is such an important patch. Thankyou so much, was having so many issues in just inference.

Thank you @gante for the pointers!

I can confirm that slow tests are passing:
```bash
# RUN_SLOW=1 pytest tests/models/qwen2_audio/test_modeling_qwen2_audio.py
...
============= 15 passed, 33 skipped in 45.03s =============
```

---

# UPDATE after seeing [failing CI](https://app.circleci.com/pipelines/github/huggingface/transformers/138686/workflows/39334258-3551-4727-9629-adcf04e95a67/jobs/1838253)

I tried different combinations of:

- keeping `all_generative_model_classes = ()` inside `Qwen2AudioForConditionalGenerationModelTest` 
- adding `GenerationTesterMixin` to inheritance list of  `Qwen2AudioForConditionalGenerationModelTest` 

```bash
# COMMAND: RUN_SLOW=1 pytest tests/models/qwen2_audio

# -- without `all_generative_model_classes = ()` and without `GenerationTesterMixin`
# -- similar to https://app.circleci.com/pipelines/github/huggingface/transformers/138686/workflows/39334258-3551-4727-9629-adcf04e95a67/jobs/1838253
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_generation_tester_mixin_inheritance - AssertionError: False is not true : This model can call `generate` from `GenerationMixin`, so one of two things must happen: 1) the tester must inherit from `GenerationTesterMixi...
==== 1 failed, 93 passed, 77 skipped, 4 warnings in 164.27s (0:02:44) =========

# -- without `all_generative_model_classes = ()` and with `GenerationTesterMixin`
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_assisted_decoding_matches_greedy_search_0_random - RuntimeError: The size of tensor a (2) must match the size of tensor b (26) at non-singleton dimension 1
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_assisted_decoding_matches_greedy_search_1_same - RuntimeError: The size of tensor a (2) must match the size of tensor b (27) at non-singleton dimension 1
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_assisted_decoding_sample - RuntimeError: The size of tensor a (2) must match the size of tensor b (27) at non-singleton dimension 1
==== 3 failed, 124 passed, 87 skipped, 4 warnings in 179.77s (0:02:59) ======

# with `all_generative_model_classes = ()` and without `GenerationTesterMixin`
==== 95 passed, 76 skipped, 4 warnings in 165.05s (0:02:45) =======
```

remaining failing tests should be fixed adding [this method](https://github.com/huggingface/transformers/blob/2936902a766b50fa6b02b28ab63b4afd9f5331f1/src/transformers/models/voxtral/modeling_voxtral.py#L527-L539) to ensure we don't trigger merging input features when not in prefil stage

run-slow: qwen2_audio

This comment contains run-slow, running the specified jobs: 

models: ['models/qwen2_audio']
quantizations: [] ...

(having a look at the CI failures, which seem unrelated to these changes)

The root issue in CI is [solved in timm](https://github.com/huggingface/pytorch-image-models/issues/2555), and [already released](https://github.com/huggingface/pytorch-image-models/releases/tag/v1.0.19). However, this release happened after we last built our CI images.

I've manually triggered a rebuild of our CI images ([here](https://github.com/huggingface/transformers/actions/runs/16484958005)), it should be a matter of waiting for this job -> rerun this PR's CI

ok, needs more work: our setup file has `"timm<=1.0.11"`, but timm==1.0.18 is installed on the CI machine

run-slow: qwen2_audio

This comment contains run-slow, running the specified jobs: 

models: ['models/qwen2_audio']
quantizations: [] ...

the CI job failed before running the slow tests, but I'm getting the following failures locally:

```
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_eager_matches_fa2_generate - RuntimeError: cu_seqlens_q must have shape (batch_size + 1)
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_eager_padding_matches_padding_free_with_position_ids - TypeError: can't assign a NoneType to a torch.cuda.LongTensor
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_flash_attention_2_padding_matches_padding_free_with_position_ids - TypeError: can't assign a NoneType to a torch.cuda.LongTensor
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_flash_attention_2_padding_matches_padding_free_with_position_ids_and_fa_kwargs - TypeError: can't assign a NoneType to a torch.cuda.LongTensor
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_flash_attn_2_inference_equivalence - RuntimeError: FlashAttention only support fp16 and bf16 data type
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_flash_attn_kernels_inference_equivalence - RuntimeError: FlashAttention only support fp16 and bf16 data type
FAILED tests/models/qwen2_audio/test_modeling_qwen2_audio.py::Qwen2AudioForConditionalGenerationModelTest::test_sdpa_padding_matches_padding_free_with_position_ids - TypeError: can't assign a NoneType to a torch.cuda.LongTensor
```

cc @ebezzam 

thanks for the update! I'll take a look into that

**[For maintainers]** Suggested jobs to run (before merge)

run-slow: qwen2_audio

run-slow: qwen2_audio

This comment contains run-slow, running the specified jobs: 

models: ['models/qwen2_audio']
quantizations: [] ...