asgi middleware for https://github.com/prometheus/client_python/issues/855

lifespan_mw.py

def strip_lifespan_events(app):
    """
    handlers/ignores lifespan events from being routed to the given app.
    """
    async def _app(scope, receive, send):
        if scope.get("type") == "lifespan":
            payload = await receive()
            await send({'type': payload['type'] + ".complete"})
            return
        await app(scope, receive, send)
    return _app