When the documented example use-case of `CountryAlpha2` is used with Mypy, it results in a type error. Code: ```python from pydantic import BaseModel from pydantic_extra_types.country import CountryAlpha2 class Product(BaseModel): made_in: CountryAlpha2 product = Product(made_in='ES') print(product) # > made_in='ES' ``` Results in: ```sh Argument "made_in" to "Product" has incompatible type "str"; expected "CountryAlpha2" [arg-type] ```