How to use the multimethod.__init__.multimethod.__get__ function in multimethod

@multimethod  # type: ignore[no-redef]
def get_type(arg: Iterable):
    """Return generic type checking first value."""
    return subtype(type(arg), *map(get_type, itertools.islice(arg, 1)))


def isa(*types) -> Callable:
    """Partially bound `isinstance`."""
    return lambda arg: isinstance(arg, types)


class overload(collections.OrderedDict):
    """Ordered functions which dispatch based on their annotated predicates."""

    __get__ = multimethod.__get__

    def __new__(cls, func):
        namespace = inspect.currentframe().f_back.f_locals
        self = functools.update_wrapper(super().__new__(cls), func)
        return namespace.get(func.__name__, self)

    def __init__(self, func: Callable):
        self[inspect.signature(func)] = func

    def __call__(self, *args, **kwargs):
        """Dispatch to first matching function."""
        for sig, func in reversed(self.items()):
            arguments = sig.bind(*args, **kwargs).arguments
            if all(predicate(arguments[name]) for name, predicate in func.__annotations__.items()):
                return func(*args, **kwargs)
        raise DispatchError("No matching functions found")