Why is it useful to pass specialized models to functions

functions_are_dry_with_models.py

from pydantic import BaseModel


class Age(BaseModel):
    __root__: int


def age_in_days(age: Age) -> int:
    return age.__root__ * 365  # 1


def test_age_in_days_only_needs_to_deal_with_ints():
    age = Age.parse_obj('42')  # 2
    assert age_in_days(age) == 42 * 365  


# note that mypy raises an error when trying the following
# will raise a mypy error
# age_in_days(age='not an age')  # 3