tests(langchain-sdk): Added unit tests for langchain SDK client and utils. (#118)

Test coverage:

| Name    | Stmts | Miss | Cover |
| -------- | ------- | ---- | ----- |
| src/toolbox_langchain_sdk/__init__.py  | 2   |  0 | 100% |
| src/toolbox_langchain_sdk/client.py | 43    | 2 | 95% |
| src/toolbox_langchain_sdk/utils.py    | 48   | 0 | 100%|
| TOTAL | 93 | 2 | 98% |

Author: twishabansal

src/toolbox_langchain_sdk/client.py

@@ -1,5 +1,5 @@
 import asyncio
-from typing import Optional, Type
+from typing import Any, Optional, Type
 
 from aiohttp import ClientSession
 from langchain_core.tools import StructuredTool
@@ -96,7 +96,7 @@ def _generate_tool(
             model_name=tool_name, schema=tool_schema.parameters
         )
 
-        async def _tool_func(**kwargs) -> dict:
+        async def _tool_func(**kwargs: Any) -> dict:
             return await _invoke_tool(self._url, self._session, tool_name, kwargs)
 
         return StructuredTool.from_function(