def handler_with_header_mods(route: Route):
route.fallback(headers={**route.request.headers, "FOO": "bar"})
def delete_foo_header(route: Route, request: Request):
headers = request.all_headers()
route.fallback(headers={**headers, "foo": None})
def handler(route: Route):
try:
route.fulfill(response=47)
except Exception:
route.fallback()