[mypy] Pass type checking in vllm/inputs

[CloseChoice]

Supports #3680 (link existing issues this PR will resolve)

I ignored the assert_never lines since this seems like an open mypy issue:

• Exhaustiveness checking fails on non-trivial use of pattern matching python/mypy#14833

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[DarkLight1337]

Can we use TypeIs here? Maybe it can avoid having to type ignore the rest of the code.

[CloseChoice]

done

[DarkLight1337]

Same comment

[CloseChoice]

done

[DarkLight1337]

Hmm, if we still need to ignore this line, then I think there isn't much point in adding those two functions...

[CloseChoice]

We need the functions here: https://github.com/vllm-project/vllm/pull/11680/files#diff-e55f6ffbb4ac8db75ad60f0b92d2ab311493184b32bb039c2d991742f53f5c56R332 to narrow down the types. Assert_never won't work since mypy expects a "Never" object here and this is still an open issue (as mentioned in the description). I just thought, since we need the functions anyway, I consistently use them everywhere but can revert where they are not used if you prefer that.

[DarkLight1337]

I mean that even after you added is_token_inputs and is_multimodal_inputs, you still have type ignore on the assert_never lines. In that case, what is the benefit of adding those two functions?

[CloseChoice]

The point is that we need to narrow down the functions to MultiModalInputsV2 here since TokenInputs does not have the "mm_hashes" key and this results then in a mypy error. So to narrow the type (actually we just need one function to narrow down to MultiModalInputsV2) I added the function and then added the other to handle these cases consistently.

[DarkLight1337]

Running mypy on the code prior to this PR, apart from assert_never I only get one additional error (vllm/inputs/data.py:314). So, I think it's better to just type ignore that extra line rather than using these two functions.

Btw, pyright passes on this file without any changes needed.

[CloseChoice]

alright, I just removed the functions and ignored the line.

[DarkLight1337]

LGTM, thanks for your contribution and patience!