This PR ties lots of loose ends in asyncio #24
Description
This PR ties lots of loose ends in asyncio so it becomes clear what is a callback (a reaction shat shouldn't be called) and what is a proper function (an action that needs to be called):
- for transports, it replaced
self._protocolwith ... to ...
In other words, currently a caller takes a callie and sticks into it each time a call in required, and after this PR a caller just calls its self._on_* without knowing about a callie that subscribed once on its creation.