Fix lint errors

optuna_dashboard/_objective_form_widget.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import warnings
 from dataclasses import dataclass
 import json
 from typing import TYPE_CHECKING
@@ -44,7 +43,9 @@ if TYPE_CHECKING:
         {"type": Literal["text"], "description": Optional[str]},
     )
     UserAttrRefJSON = TypedDict("UserAttrRefJSON", {"type": Literal["user_attr"], "key": str})
-    ObjectiveFormWidgetJSON = Union[ChoiceWidgetJSON, SliderWidgetJSON, TextInputWidgetJSON, UserAttrRefJSON]
+    ObjectiveFormWidgetJSON = Union[
+        ChoiceWidgetJSON, SliderWidgetJSON, TextInputWidgetJSON, UserAttrRefJSON
+    ]
 
 
 @dataclass
@@ -103,8 +104,9 @@ class ObjectiveUserAttrRef:
         }
 
 
-
-ObjectiveFormWidget = Union[ObjectiveChoiceWidget, ObjectiveSliderWidget, ObjectiveTextInputWidget, ObjectiveUserAttrRef]
+ObjectiveFormWidget = Union[
+    ObjectiveChoiceWidget, ObjectiveSliderWidget, ObjectiveTextInputWidget, ObjectiveUserAttrRef
+]
 SYSTEM_ATTR_KEY = "dashboard:objective_form_widgets"
 
 
@@ -112,7 +114,9 @@ def register_objective_form_widgets(study: optuna.Study, widgets: list[Objective
     if len(study.directions) != len(widgets):
         raise ValueError("The length of actions must be the same with the number of objectives.")
     widget_dicts = [w.to_dict() for w in widgets]
-    study._storage.set_study_system_attr(study._study_id, SYSTEM_ATTR_KEY, json.dumps(widget_dicts))
+    study._storage.set_study_system_attr(
+        study._study_id, SYSTEM_ATTR_KEY, json.dumps(widget_dicts)
+    )
 
 
 def get_objective_form_widgets_json(