[community] Fix WorkspaceClient error with pydantic validation (#26649)

Thank you for contributing to LangChain!

Fix error like
<img width="1167" alt="image"
src="https://github.com/user-attachments/assets/2e219b26-ec7e-48ef-8111-e0ff2f5ac4c0">

After the fix:
<img width="584" alt="image"
src="https://github.com/user-attachments/assets/48f36fe7-628c-48b6-81b2-7fe741e4ca85">


- [ ] **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, ccurme, vbarda, hwchase17.

---------

Signed-off-by: serena-ruan <serena.rxy@gmail.com>
Co-authored-by: Erick Friis <erick@langchain.dev>

libs/community/langchain_community/tools/databricks/tool.py

@@ -10,7 +10,6 @@ from pydantic import BaseModel, Field, create_model
 from typing_extensions import Self
 
 if TYPE_CHECKING:
-    from databricks.sdk import WorkspaceClient
     from databricks.sdk.service.catalog import FunctionInfo
 
 from pydantic import ConfigDict
@@ -121,7 +120,7 @@ def _get_tool_name(function: "FunctionInfo") -> str:
     return tool_name
 
 
-def _get_default_workspace_client() -> "WorkspaceClient":
+def _get_default_workspace_client() -> Any:
     try:
         from databricks.sdk import WorkspaceClient
     except ImportError as e:
@@ -137,7 +136,7 @@ class UCFunctionToolkit(BaseToolkit):
         description="The ID of a Databricks SQL Warehouse to execute functions."
     )
 
-    workspace_client: "WorkspaceClient" = Field(
+    workspace_client: Any = Field(
         default_factory=_get_default_workspace_client,
         description="Databricks workspace client.",
     )