Optional Nullable types throwing error

@connector.register_query
def foo(inp: Optional[str] = None):
print(inp)
return f"{inp}"

When you leave the type blank, it works. However, when you try to fill out the type:

query MyQuery {
foo(inp: "hey")
}

You get an error:

```
v View in Docker Deskapp_python-1 | await super().__call__(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/applications.py", line 123, in __call__
app_python-1 | await self.middleware_stack(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/middleware/errors.py", line 186, in __call__
vapp_python-1 | raise exc
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/middleware/errors.py", line 164, in __call__
app_python-1 | await self.app(scope, receive, _send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/middleware/exceptions.py", line 65, in __call__
app_python-1 | await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 64, in wrapped_app
app_python-1 | raise exc Config w Enable Watch
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
app_python-1 | await app(scope, receive, sender)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/routing.py", line 756, in __call__
app_python-1 | await self.middleware_stack(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/routing.py", line 776, in app
app_python-1 | await route.handle(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/routing.py", line 297, in handle
app_python-1 | await self.app(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/routing.py", line 77, in app
app_python-1 | await wrap_app_handling_exceptions(app, request)(scope, receive, send)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 64, in wrapped_app
app_python-1 | raise exc Config w Enable Watch
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
app_python-1 | await app(scope, receive, sender)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/starlette/routing.py", line 72, in app
app_python-1 | response = await func(request)tch
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/fastapi/routing.py", line 278, in app
app_python-1 | raw_response = await run_endpoint_function(
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/fastapi/routing.py", line 191, in run_endpoint_function
app_python-1 | return await dependant.call(**values)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/hasura_ndc/server.py", line 71, in execute_query
app_python-1 | return await instrumentation.with_active_span(
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/hasura_ndc/instrumentation.py", line 138, in with_active_span
app_python-1 | retval = await retvalEnable Watch
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/hasura_ndc/function_connector.py", line 351, in query
app_python-1 | root_args[k] = self.cast_to_type(v.value, arg_type)
app_python-1 | File "/functions/venv/lib/python3.10/site-packages/hasura_ndc/function_connector.py", line 333, in cast_to_type
app_python-1 | elif origin is not None and issubclass(origin, BaseModel):
app_python-1 | File "/usr/local/lib/python3.10/abc.py", line 123, in __subclasscheck__
app_python-1 | return _abc_subclasscheck(cls, subclass)
app_python-1 | TypeError: issubclass() arg 1 must be a class
```