Python/Types

Indicate the type of a variable, is optional.
Benefits, is warnings from editors if used wrong, or passing wrong type.

Use pydantic to validate incoming data, by creating a basemodel class.

# e.g.
from pydantic import BaseModel


class User(BaseModel):
    id: int
    name = "John Doe"
    signup_ts: Optional[datetime] = None
    friends: List[int] = []

https://fastapi.tiangolo.com/python-types/
Python/FastApi also uses pydantic + types to auto validate incoming data when building an api.