bug in APIHandler _rename_pydantic_model

[Hacky-DH]

bug at this line https://github.com/langchain-ai/langserve/blob/main/langserve/api_handler.py#L316

TypeError: issubclass() arg 1 must be a class

when I use APIHandler with different input schema runnable.

My model is

from pydantic import BaseModel
class A(BaseModel):
    foo: list[str]

pydantic use V2.

Very simple to produce issue:

>>> from pydantic import BaseModel
>>> issubclass(list,BaseModel)
False
>>> issubclass(list[str],BaseModel)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File ".../lib/python3.10/abc.py", line 123, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
TypeError: issubclass() arg 1 must be a class

[Hacky-DH]

use isinstance instead issubclass?