Setting that global const is the same as choosing between various top-level future executors. It can only be set once in a project, and it's morally equivalent

Setting that global const is the same as choosing between various top-level future executors. It can only be set once in a project, and it's morally equivalent to changing `asyncio.run()` to some other function in the python example. It just allows library writers to write async functions and have the end user choose which async impl to use.