func registerAPIRouter(router *mux.Router) {
	// Initialize API.
	api := objectAPIHandlers{
		ObjectAPI: newObjectLayerFn,
	}

	// API Router
	apiRouter := router.PathPrefix(SlashSeparator).Subrouter()

	var routers []*mux.Router
	for _, domainName := range globalDomainNames {
		if IsKubernetes() {

	healthCheckPathPrefix      = minioReservedBucketPath + healthCheckPath
)

// registerHealthCheckRouter - add handler functions for liveness and readiness routes.
func registerHealthCheckRouter(router *mux.Router) {
	// Healthcheck router
	healthRouter := router.PathPrefix(healthCheckPathPrefix).Subrouter()

	// Cluster check handler to verify cluster is active

const (
	prometheusJWT    prometheusAuthType = "jwt"
	prometheusPublic prometheusAuthType = "public"
)

// registerMetricsRouter - add handler functions for metrics.
func registerMetricsRouter(router *mux.Router) {
	// metrics router
	metricsRouter := router.NewRoute().PathPrefix(minioReservedBucketPath).Subrouter()
	authType := prometheusAuthType(strings.ToLower(env.Get(EnvPrometheusAuthType, string(prometheusJWT))))

	auth := AuthMiddleware

type adminAPIHandlers struct{}

// registerAdminRouter - Add handler functions for each service REST API routes.
func registerAdminRouter(router *mux.Router, enableConfigOps bool) {
	adminAPI := adminAPIHandlers{}
	// Admin router
	adminRouter := router.PathPrefix(adminPathPrefix).Subrouter()

	adminVersions := []string{
		adminAPIVersionPrefix,
	}

	// Add server metrics router
	registerMetricsRouter(router)

	// Add STS router always.
	registerSTSRouter(router)

	// Add KMS router
	registerKMSRouter(router)

	// Add API router
	registerAPIRouter(router)

	router.Use(globalMiddlewares...)

	return router, nil

    sub_router = APIRouter(lifespan=subrouter_lifespan)

    router = APIRouter(lifespan=router_lifespan)
    router.include_router(sub_router)

    app = FastAPI(lifespan=lifespan)
    app.include_router(router)

    @app.get("/")
    def main(request: Request) -> dict[str, str]:
        assert request.state.app
        assert request.state.router
        assert request.state.sub_router

import pytest
from fastapi import APIRouter


def test_router_circular_import():
    router = APIRouter()

    with pytest.raises(
        AssertionError,
        match="Cannot include the same APIRouter instance into itself. Did you mean to include a different router?",
    ):

from fastapi import APIRouter, FastAPI
from fastapi.testclient import TestClient


def test_redirect_slashes_enabled():
    app = FastAPI()
    router = APIRouter()

    @router.get("/hello/")
    def hello_page() -> str:
        return "Hello, World!"

    app.include_router(router)

    client = TestClient(app)

    response = client.get("/hello/", follow_redirects=False)
    assert response.status_code == 200

We are importing the submodule `items` directly, instead of importing just its variable `router`.

This is because we also have another variable named `router` in the submodule `users`.

If we had imported one after the other, like:

```Python
from .routers.items import router
from .routers.users import router
```

import pytest
from fastapi import APIRouter, FastAPI
from fastapi.exceptions import FastAPIError
from fastapi.testclient import TestClient

app = FastAPI()

router = APIRouter()


@router.get("")
def get_empty():
    return ["OK"]


app.include_router(router, prefix="/prefix")


client = TestClient(app)


def test_use_empty():
    with client:
        response = client.get("/prefix")