What is the point of `transform_parameter_types()`when it's throwing error on objects?

1

So I have a list of dictionary, i.e [{item_code: "item 1", qty: 2}] and as annotation in the method is

import frappe
from pydantic import BaseModel
from typing import List

def Item(BaseModel):
    item_code: str
    qty: float

@frappe.whitelist()
def test(items: List[Item]):
    return "OK"

When I pass the data using frappe.call() the method throws an error.