Isn't this code equivalent to yours:

async def get(process, key):
    try:
        return cache[key]
    except KeyError:
        if key in events:
            await events[key].wait()
        else:
            events[key] = asyncio.Event()

            # simulates some IO to get the Key
            await asyncio.sleep(0.1)
            cache[key] = "some random value"
            event.set()

        return cache[key]


?