filters from setup(...) has incorrect type annotation

[rkdl]

Hi, I've found a small typing issue after updating aiohttp_jinja2 from 1.1.0 to 1.2.0
mypy report:

app.py:125: error: Dict entry 0 has incompatible type "str": "Callable[[Any], str]"; expected "Callable[..., str]": "Callable[[Any], str]"

and the example code is

def statify(state) -> str:
    return json.dumps(state, ensure_ascii=False, indent=3)

aiohttp_jinja2.setup(
   app,
   loader=jinja2.FileSystemLoader('templates'),
   filters={'statify': statify},
)

PyCharm type checker also reports about typing issue

Expected type 'Optional[Iterable[(...) -> str]]', got 'Dict[str, (state: Any) -> str]' instead

The thing is, filters must be either mapping or iterable of key/value pairs, as it's passed to dict.update method, but current type annotation requires it to be a plain iterable of callables

if filters is not None:
    env.filters.update(filters)