How to use the uvicorn.importer.ImportFromStringError function in uvicorn

def test_invalid_format():
    with pytest.raises(ImportFromStringError) as exc:
        import_from_string("example:")
    expected = 'Import string "example:" must be in format ":".'
    assert expected in str(exc)

def test_invalid_module():
    with pytest.raises(ImportFromStringError) as exc:
        import_from_string("module_does_not_exist:myattr")
    expected = 'Could not import module "module_does_not_exist".'
    assert expected in str(exc)

try:
        module = importlib.import_module(module_str)
    except ImportError as exc:
        if exc.name != module_str:
            raise exc from None
        message = 'Could not import module "{module_str}".'
        raise ImportFromStringError(message.format(module_str=module_str))

    instance = module
    try:
        for attr_str in attrs_str.split("."):
            instance = getattr(instance, attr_str)
    except AttributeError as exc:
        message = 'Attribute "{attrs_str}" not found in module "{module_str}".'
        raise ImportFromStringError(
            message.format(attrs_str=attrs_str, module_str=module_str)
        )

    return instance

if isinstance(self.http, str):
            self.http_protocol_class = import_from_string(HTTP_PROTOCOLS[self.http])
        else:
            self.http_protocol_class = self.http

        if isinstance(self.ws, str):
            self.ws_protocol_class = import_from_string(WS_PROTOCOLS[self.ws])
        else:
            self.ws_protocol_class = self.ws

        self.lifespan_class = import_from_string(LIFESPAN[self.lifespan])

        try:
            self.loaded_app = import_from_string(self.app)
        except ImportFromStringError as exc:
            logger.error("Error loading ASGI app. %s" % exc)
            sys.exit(1)

        if self.interface == "auto":
            if inspect.isclass(self.loaded_app):
                use_asgi_3 = hasattr(self.loaded_app, "__await__")
            elif inspect.isfunction(self.loaded_app):
                use_asgi_3 = asyncio.iscoroutinefunction(self.loaded_app)
            else:
                call = getattr(self.loaded_app, "__call__", None)
                use_asgi_3 = asyncio.iscoroutinefunction(call)
            self.interface = "asgi3" if use_asgi_3 else "asgi2"

        if self.interface == "wsgi":
            self.loaded_app = WSGIMiddleware(self.loaded_app)
            self.ws_protocol_class = None