ASGI lifespan crash

client_python version: testing on 0.15.0 but the offending code exists in the master branch as well.

I'm trying to use the prometheus ASGI handler with Hypercorns DispatcherMiddleware. It sends lifecycle events which are not properly handled:

def make_asgi_app(registry: CollectorRegistry = REGISTRY, disable_compression: bool = False) -> Callable:
    """Create a ASGI app which serves the metrics from a registry."""

    async def prometheus_app(scope, receive, send):
        assert scope.get("type") == "http"
        # Prepare parameters

assert scope.get("type") == "http" ensures any ASGI middleware sending lifecycle events will fail to start the prometheus asgi app.

从 make_asgi_app 函数及其关于 ASGI scope 类型为 http 的断言开始。使用 Prometheus ASGI handler 和 Hypercorn 的 DispatcherMiddleware（包括其生命周期事件）复现该失败。完成标准是：生命周期事件不再导致启动崩溃，同时 handler 仍能处理 metrics 请求。