Repository: langchain
Issue: Error during FAISS save_local due to __pydantic_private__ attribute
Labels: Ɑ: vector store,stale

### Checked other resources

- [X] I added a very descriptive title to this issue.
- [X] I searched the LangChain documentation with the integrated search.
- [X] I used the GitHub search to find a similar question and didn't find it.
- [X] I am sure that this is a bug in LangChain rather than my code.
- [X] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

### Example Code

```from langchain_community.vectorstores import FAISS
from langchain_community.embeddings import GoogleGenerativeAIEmbeddings

embeddings = GoogleGenerativeAIEmbeddings(model="models/embedding-001")

print(f'Loading FAISS index from temp directory: {temp_dir}')
self.vector_store = FAISS.load_local(temp_dir, embeddings=embeddings, allow_dangerous_deserialization=True)
print("Successfully Loaded the vector store")
self.vector_store.add_texts(text_chunks)
print("Updated the vector store")

cloud_path_to_delete = f"/tmp/{uid}/{client_organization_id}/{grant_proposal_form_id}"
self.delete_directory_in_cloud(self.upload_bucket_name, cloud_path_to_delete)
print("Successfully deleted the Faiss_index")

print(f"Vector store attributes before saving:{vars(self.vector_store)}")
updated_faiss_path = f"/tmp/{uid}/{client_organization_id}/{grant_proposal_form_id}"
try:
    self.vector_store.save_local(updated_faiss_path)
    print("Successfully saved the updated Faiss Index")
except Exception as e:
    print(f"Error during FAISS save_local:{e}")
self.upload_Vector_DB_files(self.upload_bucket_name, updated_faiss_path)
```

### Error Message and Stack Trace (if applicable)

_No response_

### Description

I am experiencing an error when attempting to save the FAISS vector store using the `save_local()` method from the `langchain_community` library using google cloud run functions. The error is related to the `__pydantic_private__` attribute, which appears to be causing a serialization issue. 

**Steps to Reproduce**:
1. Create a FAISS vector store using the `FAISS.from_texts()` method with embeddings provided by `GoogleGenerativeAIEmbeddings`.
2. Attempt to save the vector store using the `save_local()` method.
3. The error is encountered during the saving process.

**Expected Behavior**:
The vector store should be saved without serialization issues.

**Actual Behavior**:
The following error is raised:
Error during FAISS save_local: pydantic_private

```
AttributeError: __pydantic_private__

at .__getattr__ ( /layers/google.python.pip/pip/lib/python3.9/site-packages/pydantic/main.py:853 )
at .__getstate__ ( /layers/google.python.pip/pip/lib/python3.9/site-packages/pydantic/main.py:942 )
at .save_local ( /layers/google.python.pip/pip/lib/python3.9/site-packages/langchain_community/vectorstores/faiss.py:1162 )
at .download_and_initialize_vectorStore_fromGC ( /workspace/VectorStoreUpdateTrigger.py:106 )
at .get_vector_store ( /workspace/VectorStoreUpdateTrigger.py:124 )
at .process_file ( /workspace/main.py:54 )
at .process_new_file ( /workspace/main.py:25 )
at .view_func ( /layers/google.python.pip/pip/lib/python3.9/site-packages/functions_framework/__init__.py:237 )
at .wrapper ( /layers/google.python.pip/pip/lib/python3.9/site-packages/functions_framework/execution_id.py:106 )
at .dispatch_request ( /layers/google.python.pip/pip/lib/python3.9/site-packages/flask/app.py:1799 )
at .full_dispatch_request ( /layers/google.python.pip/pip/lib/python3.9/site-packages/flask/app.py:1823 )
at .full_dispatch_request ( /layers/google.python.pip/pip/lib/python3.9/site-packages/flask/app.py:1825 )
at .wsgi_app ( /layers/google.python.pip/pip/lib/python3.9/site-packages/flask/app.py:2529 )```

### System Info

System Information
------------------
> OS:  Linux
> OS Version:  #1 SMP Sun Jan 10 15:06:54 PST 2016
> Python Version:  3.9.20 (main, Sep  8 2024, 05:08:52) 
[GCC 7.5.0]

Package Information
-------------------
> langchain_core: 0.3.12
> langchain: 0.3.4
> langchain_community: 0.3.3
> langsmith: 0.1.137
> langchain_google_genai: 2.0.1
> langchain_text_splitters: 0.3.0

Optional packages not installed
-------------------------------
> langgraph
> langserve

Other Dependencies
------------------
> aiohttp: 3.10.10
> async-timeout: 4.0.3
> dataclasses-json: 0.6.7
> google-generativeai: 0.8.3
> httpx: 0.27.2
> jsonpatch: 1.33
> numpy: 1.26.4
> orjson: 3.10.10
> packaging: 24.1
> pillow: Installed. No version info available.
> pydantic: 2.9.2
> pydantic-settings: 2.6.0
> PyYAML: 6.0.2
> requests: 2.32.3
> requests-toolbelt: 1.0.0
> SQLAlchemy: 2.0.36
> tenacity: 9.0.0
> typing-extensions: 4.12.2