Improve error message

[Yanni8]

Checked

• I searched existing ideas and did not find a similar one
• I added a very descriptive title
• I've clearly described the feature request and motivation for it

Feature request

I just got the following error

ValidationError: 1 validation error for StructuredTool args_schema subclass of BaseModel expected (type=type_error.subclass; expected_class=BaseModel)

But this didn't realy make any sense to me since my schema class was a sublcase of BaseModel.

from pydantic import BaseModel

class MySchema(BaseModel):
    pass

I then figured out after reading the documentation again that Langchain was expecting a Subclass of langchain.pydantic_v1.BaseModel

Maybe we should update the error message to make it more clear that langchain doesn't expect the pydantic.BaseModel class.

Motivation

Make the error message clearer to prevent the user creating a bug that are hard to solve.

Proposal (If applicable)

Maybe update the error message to something like

ValidationError: 1 validation error for StructuredTool args_schema subclass of `langchain.pydantic_v1.BaseModel` expected (type=type_error.subclass; expected_class=langchain.pydantic_v1.BaseModel)