mypy: protocol + bound

nouns.py

from typing import Protocol, TypeVar


class Record:
    """in practice, this class has many more methods/
    attributes that I need access to."""
    def update(self):
        pass


class Person(Record):
    first_name: str
    last_name: str
    address: str
    lon: float
    lat: float


class Place(Record):
    name: str
    address: str
    long: float
    lat: float


class Thing:
    name: str


class Geocode(Protocol):
    address: str
    lon: float
    lat: float

# this is the part I don't know how to do
# basically, I want to say that a GeocodableRecord is fully a record,
# but one which definitely has these specific attributes.
GeocodableRecord = TypeVar("GeocodableRecord", bound=[Geocode, Record])


def geocode(a: GeocodableRecord):
    lon, lat = do_geocode(a.address)
    a.lon = lon
    a.lat = lat
    a.update()