fix the lint error in backend

backend/tests/test_thread_run_messages_pagination.py

@@ -1,15 +1,14 @@
 """Tests for paginated GET /api/threads/{thread_id}/runs/{run_id}/messages endpoint."""
+
 from __future__ import annotations
 
 from unittest.mock import AsyncMock, MagicMock
 
-import pytest
 from _router_auth_helpers import make_authed_test_app
 from fastapi.testclient import TestClient
 
 from app.gateway.routers import thread_runs
 
-
 # ---------------------------------------------------------------------------
 # Helpers
 # ---------------------------------------------------------------------------
@@ -78,7 +77,8 @@ def test_after_seq_forwarded_to_event_store():
         response = client.get("/api/threads/thread-3/runs/run-3/messages?after_seq=5")
     assert response.status_code == 200
     event_store.list_messages_by_run.assert_awaited_once_with(
-        "thread-3", "run-3",
+        "thread-3",
+        "run-3",
         limit=51,  # default limit(50) + 1
         before_seq=None,
         after_seq=5,
@@ -94,7 +94,8 @@ def test_before_seq_forwarded_to_event_store():
         response = client.get("/api/threads/thread-4/runs/run-4/messages?before_seq=10")
     assert response.status_code == 200
     event_store.list_messages_by_run.assert_awaited_once_with(
-        "thread-4", "run-4",
+        "thread-4",
+        "run-4",
         limit=51,
         before_seq=10,
         after_seq=None,
@@ -110,7 +111,8 @@ def test_custom_limit_forwarded_to_event_store():
         response = client.get("/api/threads/thread-5/runs/run-5/messages?limit=10")
     assert response.status_code == 200
     event_store.list_messages_by_run.assert_awaited_once_with(
-        "thread-5", "run-5",
+        "thread-5",
+        "run-5",
         limit=11,  # 10 + 1
         before_seq=None,
         after_seq=None,