[V1] Change return type on get_multimodal_embeddings()

[russellb]

The return type implied that None was a valid return value, but the
code does not treat it that way. sanity_check_mm_encoder_outputs() in
vllm.v1.worker.utils is called on the output and does not allow None.

While we're at it, also change the input parameter type to the sanity
check function. Previously, it was specified as object, but it should
be MultiModalEmbeddings.

Implementations of the method can still return an empty list if
necessary.

Signed-off-by: Russell Bryant rbryant@redhat.com

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[gemini-code-assist]

Summary of Changes

Hello @russellb, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses type hint inaccuracies related to multimodal embeddings. The get_multimodal_embeddings method was incorrectly marked as potentially returning None, while downstream code expected a MultiModalEmbeddings object. This change updates the type hints to accurately reflect the code's behavior and improves type safety.

Highlights

• Type Hint Correction: Corrected the return type hint for the get_multimodal_embeddings method across various model implementations and the SupportsMultiModal interface from Optional[MultiModalEmbeddings] to MultiModalEmbeddings.
• Sanity Check Type Update: Updated the type hint for the mm_embeddings parameter in the sanity_check_mm_encoder_outputs function to MultiModalEmbeddings, aligning it with the expected input type.

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[gemini-code-assist]

Code Review

This pull request correctly identifies and addresses an inconsistency in the return type of get_multimodal_embeddings. By removing Optional from the return type and updating the sanity_check_mm_encoder_outputs function to expect MultiModalEmbeddings, the type hints become more precise and align better with the actual usage.

The primary feedback is to ensure that all implementations of get_multimodal_embeddings that previously returned None are updated to return an empty list ([]) to conform to the new non-optional type hint, as implied by the PR description. This will prevent potential type errors and ensure consistency across all multimodal models.

[ywang96]

Thanks for fixing! The code change makes sense to me. cc @DarkLight1337 if you want to take a look too.

[russellb]

It looks like this broke some multi-modal tests. I'll take a look.

[maxdebayser]

@russellb, this commit is breaking tests like samplers/test_beam_search.py::test_beam_search_passes_multimodal_data because in a lot of places like

vllm/vllm/model_executor/models/qwen2_audio.py

Line 367 in 90f9c2e

if multimodal_embeddings is not None:

because they still compare the multimodal inputs with None.

[russellb]

@russellb, this commit is breaking tests like samplers/test_beam_search.py::test_beam_search_passes_multimodal_data because in a lot of places like

vllm/vllm/model_executor/models/qwen2_audio.py

Line 367 in 90f9c2e

if multimodal_embeddings is not None:

because they still compare the multimodal inputs with None.

I guess these tests aren't running in CI always since CI was green here? Sorry for the trouble.

[russellb]

I'm working on fixes.

[russellb]

follow up here: #19715