fix: add warnings for duplicated or conflicting type hints in bigfram…

[jialuoo]

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Fixes b/409565963.

[TrevorBergeron]

Maybe we should just warn if the decorator actually conflicts with the signature?

[jialuoo]

Maybe we should just warn if the decorator actually conflicts with the signature?

I considered that. While warning only on a signature conflict is an option, I'm concerned about the risk of users defining type hints in both the decorator and the function signature. Since this is just a warning and won't fail the execution, I lean toward warning users about any duplicated type hints too. What do you think?