My latest suggestion to Yury was to see how the PEP reads with it
called ImplicitContext, such that:

* the active execution context is a stack of implicit contexts
* ContextKey.set() updates the innermost implicit context
* Contextkey.get() reads the whole stack of active implicit contexts
* by default, generators (both sync and async) would have their own
implicit context, but you could make them use the context of method
callers by doing "gen.__implicit_context__ = None"
* by default, coroutines would use their method caller's context, but
async frameworks would make sure to give top-level tasks their own
independent contexts

That proposal came from an initial attempt at redrafting the Abstract
and Rationale sections, where it turns out that one of the things the
current version of the PEP is somewhat taking for granted is that the
reader already has a particular understanding of the difference
between explicit state management (i.e. passing things around as
function arguments and instance attributes) and implicit state
management (i.e. relying on process globals and thread locals).