diff --git a/recipes/001_first.py b/recipes/001_first.py
index 915ea10c..0ad3085a 100644
--- a/recipes/001_first.py
+++ b/recipes/001_first.py
@@ -150,6 +150,7 @@ def plot_optimizaiton_history(study: optuna.study.Study) -> go.Figure:
     return fig
 
 
+###################################################################################################
 # If you use `matplotlib` (https://matplotlib.org/) for visualization, the function should return a `matplotlib.figure.Figure` object.