def all_literal_values(type_: Type[Any]) -> Tuple[Any, ...]:
    """
    This method is used to retrieve all Literal values as
    Literal can be used recursively (see https://www.python.org/dev/peps/pep-0586)
    e.g. `Literal[Literal[Literal[1, 2, 3], "foo"], 5, None]`
    """
    if not is_literal_type(type_):
        return (type_,)

    values = literal_values(type_)
    return tuple(x for value in values for x in all_literal_values(value))

    This method is used to retrieve all Literal values as
    Literal can be used recursively (see https://www.python.org/dev/peps/pep-0586)
    e.g. `Literal[Literal[Literal[1, 2, 3], "foo"], 5, None]`
    
pydantic/v1/typing.py