*
   * @param <V1> the type returned by the first future
   * @param <V2> the type returned by the second future
   * @param <V3> the type returned by the third future
   * @param <V4> the type returned by the fourth future
   */
  public static final class Combiner4<
          V1 extends @Nullable Object,
          V2 extends @Nullable Object,
          V3 extends @Nullable Object,
          V4 extends @Nullable Object>

    app = FastAPI()
    router = APIRouter()


    @router.get("/users/", tags=["users"])
    async def read_users():
        return [{"username": "Rick"}, {"username": "Morty"}]


    app.include_router(router)
    ```
    """

    def __init__(
        self,
        *,
        prefix: Annotated[str, Doc("An optional path prefix for the router.")] = "",