langchain: allow CacheBackedEmbeddings to cache queries

[jokester]

Thank you for contributing to LangChain!

• PR title: "package: description"

  • Where "package" is whichever of langchain, community, core, experimental, etc. is being modified. Use "docs: ..." for purely docs changes, "templates: ..." for template changes, "infra: ..." for CI changes.
  • Example: "community: add foobar LLM"

• Description:

This PR allow cache of query embedding. Prior to this PR, it required a custom class to cache queries too.
To make the change non-breaking, query caching is not enabled by default.

• Issue: no, but an intent was mentioned in docs: mention caveats with CacheBackedEmbeddings.embed_query #19926

• Dependencies: no

• **Twitter handle: tarsylia

• Add tests and docs: If you're adding a new integration, please include

  1. a test for the integration, preferably unit tests that do not rely on network access,
  2. an example notebook showing its use. It lives in docs/docs/integrations directory.

• Lint and test: Run make format, make lint and make test from the root of the package(s) you've modified. See contribution guidelines for more: https://python.langchain.com/docs/contributing/

Additional guidelines:

• Make sure optional dependencies are imported within a function.
• Please do not add dependencies to pyproject.toml files (even optional ones) unless they are required for unit tests.
• Most PRs should not touch more than one package.
• Changes should be backwards compatible.
• If you are adding something to community, do not re-import it in langchain.

If no one reviews your PR within a few days, please @-mention one of baskaryan, efriis, eyurtsev, hwchase17.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
langchain	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 13, 2024 3:17pm

[jokester]

@eyurtsev Sorry to bother but can I ask you to review this too? 🙏🏽

I think this PR answers some concern in previous code comments and also make it easier to use.

[eyurtsev]

Looks great! Merging