Added support to get usage for ChatGoogleGenerativeAI

[NeerajG03]

This PR has been raised to add support to track ChatGoogleGenerativeAI's langchain call usage. A simple check for usage_metadata attribute and then parsing using the _parse_usage_model

[CLAassistant]

All committers have signed the CLA.

[maxdeichmann]

@NeerajG03 did you test this locally? Thanks a lot for the contribution!

[NeerajG03]

@maxdeichmann I'm sorry i'm very new to contributing for projects. If you are asking if i have run this test poetry run pytest -s -v --log-cli-level=INFO, then thats a yes. 👍 I ran it for test_langchain.py and test_langchain_integration.py

[NeerajG03]

Here is the screenshot of the run summary

[aunitt]

This also worked for me for ChatVertexAI.

It appears to fix my issues which appear to be those mentioned in https://github.com/langfuse/langfuse/issues/5468

[hassiebp]

Thanks again for raising this! Closing this as stale / no longer relevant in Python SDK v3. If you continue to see issues, please open a Github issue 👍🏾