feat(core): add 'approximate' alias in place of count_tokens_approximately

[Davda-James]

Description:

earlier we have to use like below:

from langchain_core.messages import trim_messages
from langchain_core.messages.utils import count_tokens_approximately

trim_messages(..., token_counter=count_tokens_approximately)

Now can be used as like this also

from langchain_core.messages import trim_messages

trim_messages(..., token_counter="approximate")

• Added tests
• Lint and test: Run this as I made change in langchain/core, uv run --group test pytest tests/unit_tests/messages/test_utils.py -v

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
langchain	Ignored	Preview		Sep 26, 2025 7:37pm

[codspeed-hq]

CodSpeed Performance Report

Merging #33045 will not alter performance

_{Comparing Davda-James:feat/trim_messages-support-approx-alias (0834892) with master (72f1d79)}

⚠️ 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.

Summary

✅ 13 untouched
⏩ 21 skipped¹

Footnotes

1. 21 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. ↩

[eyurtsev]

@Davda-James could you undo the changes in the lock file? And we can merge then?

[Davda-James]

@eyurtsev reverted the lock file changes in new commit.

[Davda-James]

Hey @eyurtsev any further changes needed or anything to add ?