Fix return annotation of Observable.__await__

[giff-h]

This fixes issues with mypy type checking when awaiting an observable

Here is an example output from await subject on mypy 0.940 (latest at time of PR opening)

tests/reactive/test_api_direct.py:1564: error: Incompatible types in "await" (actual type "Subject[Dict[str, Any]]", expected type "Awaitable[Any]")  [misc]
tests/reactive/test_api_direct.py:1564: note: Following member(s) of "Subject[Dict[str, Any]]" have conflicts:
tests/reactive/test_api_direct.py:1564: note:     Expected:
tests/reactive/test_api_direct.py:1564: note:         def __await__(self) -> Generator[Any, None, Any]
tests/reactive/test_api_direct.py:1564: note:     Got:
tests/reactive/test_api_direct.py:1564: note:         def __await__(self) -> Iterable[Dict[str, Any]]

[coveralls]

Coverage increased (+0.0003%) to 93.363% when pulling 59beb65 on hamstap85:observable-await-typing into 3130ffc on ReactiveX:master.

[dbrattli]

Thanks for fixing this. Please ensure that you follow the developer guidelines before submitting a PR or you will need to make a lot of small fixes to get this passing the code checks i.e black, isort, ... Also note that generic Future is not supported in older versions of Python so you need to string the type i.e "Future[_T]"

[giff-h]

@dbrattli Ah I thought that would get handled with from __future__ import annotations, I'll get an environment set up for local development tomorrow and fix it. I made this edit in the web editor so I didn't have a full setup yet.

Also I made the switch_map operator because I needed it for my current project, drawing inspiration from the definition in rxjs, if you'd like me to submit a draft for that.

[dbrattli]

@hamstap85 You are right about from __future__ import annotations fixing this.

[dbrattli]

Please feel free to submit a PR for switch_map with tests and docs

[giff-h]

@dbrattli updated

[dbrattli]

Thanks for fixing!