diff --git a/optuna_dashboard/_form_widget.py b/optuna_dashboard/_form_widget.py
index 2b97af48..d9a80b69 100644
--- a/optuna_dashboard/_form_widget.py
+++ b/optuna_dashboard/_form_widget.py
@@ -72,6 +72,9 @@ class ChoiceWidget:
     Example:
         .. code-block:: python
 
+            from optuna_dashboard import ChoiceWidget
+
+
             choice_widget = ChoiceWidget(
                 choices=["A", "B", "C"], values=[1.0, 2.0, 3.0], description="Choose one"
             )
@@ -123,6 +126,9 @@ class SliderWidget:
     Example:
         .. code-block:: python
 
+            from optuna_dashboard import SliderWidget
+
+
             slide_widget = SliderWidget(min=0, max=10, step=1, description="Example slider")
     """
 
@@ -181,6 +187,9 @@ class TextInputWidget:
     Example:
         .. code-block:: python
 
+            from optuna_dashboard import TextInputWidget
+
+
             text_input = TextInputWidget(description="Text Input Example")
     """
 
@@ -222,6 +231,9 @@ class ObjectiveUserAttrRef:
     Example:
         .. code-block:: python
 
+            from optuna_dashboard import ObjectiveUserAttrRef
+
+
             user_attr_ref = ObjectiveUserAttrRef(key="key")
     """