Fix linter

optuna_dashboard/preferential/_system_attrs.py

@@ -67,7 +67,7 @@ def get_skipped_trial_ids(study_system_attrs: dict[str, Any]) -> list[int]:
         if not k.startswith(_SYSTEM_ATTR_PREFIX_SKIP_TRIAL):
             continue
         try:
-            trial_id = int(k[len(_SYSTEM_ATTR_PREFIX_SKIP_TRIAL) :])
+            trial_id = int(k[len(_SYSTEM_ATTR_PREFIX_SKIP_TRIAL) :])  # noqa: E203
             skipped_trial_ids.append(trial_id)
         except ValueError:
             continue

python_tests/test_api.py

@@ -160,7 +160,7 @@ class APITestCase(TestCase):
         storage = optuna.storages.InMemoryStorage()
         study = create_study(storage=storage, n_generate=3)
         for _ in range(3):
-            trial = study.ask()
+            study.ask()
 
         app = create_app(storage)
         study_id = study._study._study_id