if (forward_input) {
    TFE_DeleteTensorHandle(n);
  }

  int num_retvals = 1;
  if (async) {
    // Enqueue dummy ops so we backlog async execution & actually test async.
    // This is usually unnecessary, but we've experienced the occasional test
    // failure when testing async mode with no explicit forwarding.
    for (int i = 0; i < 100000; ++i) {
      TFE_Op* add_op_dummy = AddOp(ctx, m, m);

async def routerindexparams(websocket: WebSocket, pathparam: str, queryparam: str):
    await websocket.accept()
    await websocket.send_text(pathparam)
    await websocket.send_text(queryparam)
    await websocket.close()


async def ws_dependency():
    return "Socket Dependency"


@router.websocket("/router-ws-depends/")
async def router_ws_decorator_depends(
    websocket: WebSocket, data=Depends(ws_dependency)

namespace {

void TestRemoteExecuteSilentCopiesFunc(bool async, bool remote,
                                       bool heavy_load_on_streaming_rpc,
                                       bool remote_func_outputs = false,
                                       bool has_packed_input = false) {
  return TestRemoteExecuteSilentCopies(async, remote, /*func=*/true,
                                       heavy_load_on_streaming_rpc,

        monkeypatch.delattr("multipart.multipart.parse_options_header", raising=False)
    with pytest.raises(RuntimeError, match=multipart_incorrect_install_error):
        app = FastAPI()

        @app.post("/")
        async def root(username: str = Form()):
            return username  # pragma: nocover


def test_incorrect_multipart_installed_file_upload(monkeypatch):
    monkeypatch.setattr("python_multipart.__version__", "0.0.12")

      : status_(TF_NewStatus()),
        // If the context's default exector is set to async, re-using that in
        // each thread would cause collectives to deadlock. For consistency we
        // create a new sync executor for every thread.
        //
        // TODO(allenl): We should have an async API that works with the
        // parallel device.
        device_(device),
        executor_(

def test_merged_mixed_state_lifespans() -> None:
    @asynccontextmanager
    async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    @asynccontextmanager
    async def router_lifespan(app: FastAPI) -> AsyncGenerator[Dict[str, bool], None]:
        yield {"router": True}

    @asynccontextmanager
    async def sub_router_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    @app.post("/files/")
    async def create_file(file: Annotated[bytes, File()]):
        return {"file_size": len(file)}


    @app.post("/uploadfile/")
    async def create_upload_file(file: UploadFile):
        return {"filename": file.filename}
    ```
    """

    file: Annotated[
        BinaryIO,
        Doc("The standard Python file object (non-async)."),
    ]

The first thing to notice, is that we are defining an async function with `yield`. This is very similar to Dependencies with `yield`.

{* ../../docs_src/events/tutorial003.py hl[14:19] *}

The first part of the function, before the `yield`, will be executed **before** the application starts.

And the part after the `yield` will be executed **after** the application has finished.

### Async Context Manager

        @app.get("/items/{item_id}/")
        async def get_item(item_id: Annotated[int, Path(default=1)]):
            pass  # pragma: nocover

    with pytest.raises(
        AssertionError,
        match=(
            "`Query` default value cannot be set in `Annotated` for 'item_id'. Set the"
            " default value with `=` instead."
        ),
    ):

        @app.get("/")

from fastapi import Depends, FastAPI, Header, HTTPException
from typing_extensions import Annotated


async def verify_token(x_token: Annotated[str, Header()]):
    if x_token != "fake-super-secret-token":
        raise HTTPException(status_code=400, detail="X-Token header invalid")


async def verify_key(x_key: Annotated[str, Header()]):
    if x_key != "fake-super-secret-key":
        raise HTTPException(status_code=400, detail="X-Key header invalid")