fix(core): add missing -> None return type to Tee.__init__() in iter …

[Debashish Mohapatra (debashish-datascience1)]

Summary

Added missing -> None return type annotation to Tee.__init__()
in langchain_core/utils/iter.py for both sync and async implementations.

Changes

• Added -> None return type to Tee.__init__()
• Added -> None return type to Tee.__aiter__()

Why

Improves type safety and consistency with Python typing best practices.
No functional changes — annotation fix only.

Testing

No tests required — this is a type annotation fix only.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 13 untouched benchmarks
⏩ 23 skipped benchmarks¹

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_{Comparing debashish-datascience1:fix/my-contribution (d26c0fa) with master (fcca6e2)²}

Footnotes

1. 23 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on master (7cef35b) during the generation of this report, so fcca6e2 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩