diff --git a/obsidian/campaign/explainer.py b/obsidian/campaign/explainer.py
index 5c7709c..ef512a6 100644
--- a/obsidian/campaign/explainer.py
+++ b/obsidian/campaign/explainer.py
@@ -67,7 +67,7 @@ def shap_explain(self,
         Args:
             responseid (int): Index of the target response variable.
             n (int): Number of samples to generate for shap values.
-            X_ref (pd.DataFrame | None, optional): Reference DataFrame for shap values. 
+            X_ref (pd.DataFrame | None, optional): Reference DataFrame for shap values.
                 If None, the ``self.optimizer.X_best_f`` will be used. Defaults to ``None``.
             seed (int | None): Seed value for random number generation.