refactor: Move type-only imports into TYPE_CHECKING blocks

Move imports that are only used for type annotations into TYPE_CHECKING
blocks to prevent unnecessary runtime imports and potential circular
import issues.

Changes:
- fastapi/openapi/utils.py: Response
- tests/test_dependency_contextmanager.py: StreamingResponse
- tests/test_route_scope.py: APIRoute

Detected via: ruff check . --select TC002

fastapi/openapi/utils.py

@@ -3,7 +3,7 @@ import http.client
 import inspect
 import warnings
 from collections.abc import Sequence
-from typing import Any, Literal, cast
+from typing import Any, Literal, cast, TYPE_CHECKING
 
 from fastapi import routing
 from fastapi._compat import (
@@ -27,7 +27,6 @@ from fastapi.exceptions import FastAPIDeprecationWarning
 from fastapi.openapi.constants import METHODS_WITH_BODY, REF_PREFIX
 from fastapi.openapi.models import OpenAPI
 from fastapi.params import Body, ParamTypes
-from fastapi.responses import Response
 from fastapi.sse import _SSE_EVENT_SCHEMA
 from fastapi.types import ModelNameMap
 from fastapi.utils import (
@@ -39,6 +38,9 @@ from pydantic import BaseModel
 from starlette.responses import JSONResponse
 from starlette.routing import BaseRoute
 
+if TYPE_CHECKING:
+    from fastapi.responses import Response
+
 validation_error_definition = {
     "title": "ValidationError",
     "type": "object",

tests/test_dependency_contextmanager.py

@@ -2,8 +2,11 @@ import json
 
 import pytest
 from fastapi import BackgroundTasks, Depends, FastAPI
-from fastapi.responses import StreamingResponse
 from fastapi.testclient import TestClient
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from fastapi.responses import StreamingResponse
 
 app = FastAPI()
 state = {

tests/test_route_scope.py

@@ -1,7 +1,10 @@
 import pytest
 from fastapi import FastAPI, Request, WebSocket, WebSocketDisconnect
-from fastapi.routing import APIRoute, APIWebSocketRoute
 from fastapi.testclient import TestClient
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from fastapi.routing import APIRoute, APIWebSocketRoute
 
 app = FastAPI()