How to create a discardable generic

throwable_generic.py

# https://stackoverflow.com/questions/67803260
from typing import Generic, TypeVar, Dict, Any, Union

class DataClassJsonMixin: ...
class Person(DataClassJsonMixin): ...
JSON = Dict[str, Any]  # Good enough json type for this demo
T = TypeVar("T", bound=DataClassJsonMixin)

# Solution 1: Union with impossible type that takes a Generic
# JSONOf = Union[JSON, Dict[JSON, T]]

# Solution 2: Union with custom generic class
class JSONFrom(Generic[T]):
    # just a crude failsafe to prohibit instantiation
    # could be improved with __new__, __init_subclasses__, etc
    def __init__(self):
        raise TypeError("Just dont!")

JSONOf = Union[JSON, JSONFrom[T]]

def add_person_to_db(person: JSONOf[Person]):
    print(person)
    try: reveal_type(person)
    except NameError: pass

add_person_to_db({'id': 1234, 'name': 'Someone'})  # Checks
add_person_to_db("Not a JSON")       # Check error by JSON
add_person_to_db(Person())           # Make sure it does not accept Person
try: someone: JSONFrom = JSONFrom()  # Make sure it does not accept JSONFrom
except TypeError as e: print(e)      # Nice try!