[Async-sig] async documentation methods

[Dima Tisnek]

Hi all,

I'm working to improve async docs, and I wonder if/how async methods
ought to be marked in the documentation, for example
library/async-sync.rst:

""" ... It [lock] has two basic methods, `acquire()` and `release()`. ... """

In fact, these methods are not symmetric, the earlier is asynchronous
and the latter synchronous:

Definitions are `async def acquire()` and `def release()`.
Likewise user is expected to call `await .acquire()` and `.release()`.

This is user-facing documentation, IMO it should be clearer.
Although there are examples for this specific case, I'm concerned with
general documentation best practice.

Should this example read, e.g.:
* two methods, `async acquire()` and `release()`
or perhaps
* two methods, used `await x.acquire()` and `x.release()`
or something else?

If there's a good example already Python docs or in some 3rd party
docs, please tell.

Likewise, should there be marks on iterators? async generators? things
that ought to be used as context managers?

Cheers,
d.