Use a submodule for pydantic v1 compat (#9371)

<!-- Thank you for contributing to LangChain!

Replace this entire comment with:
  - Description: a description of the change, 
  - Issue: the issue # it fixes (if applicable),
  - Dependencies: any dependencies required for this change,
- Tag maintainer: for a quicker response, tag the relevant maintainer
(see below),
- Twitter handle: we announce bigger features on Twitter. If your PR
gets announced and you'd like a mention, we'll gladly shout you out!

Please make sure your PR is passing linting and testing before
submitting. Run `make format`, `make lint` and `make test` to check this
locally.

See contribution guidelines for more information on how to write/run
tests, lint, etc:

https://github.com/hwchase17/langchain/blob/master/.github/CONTRIBUTING.md

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. These live is docs/extras
directory.

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

libs/experimental/langchain_experimental/cpal/models.py

@@ -6,9 +6,15 @@ from typing import Any, Optional, Union
 import duckdb
 import pandas as pd
 from langchain.graphs.networkx_graph import NetworkxEntityGraph
-from pydantic_v1 import BaseModel, Field, PrivateAttr, root_validator, validator
 
 from langchain_experimental.cpal.constants import Constant
+from langchain_experimental.pydantic_v1 import (
+    BaseModel,
+    Field,
+    PrivateAttr,
+    root_validator,
+    validator,
+)
 
 
 class NarrativeModel(BaseModel):