diff --git a/rdstar/offline_analysis/fitting/dedicated_fit_approach/systematics_manager/shape_sys_evaluater.py b/rdstar/offline_analysis/fitting/dedicated_fit_approach/systematics_manager/shape_sys_evaluater.py
index 6c437e758c06ac64f493ef5c52b462316d21d23d..c2bf3d4c34513cae071ae9d64facd7ad1b4d5318 100644
--- a/rdstar/offline_analysis/fitting/dedicated_fit_approach/systematics_manager/shape_sys_evaluater.py
+++ b/rdstar/offline_analysis/fitting/dedicated_fit_approach/systematics_manager/shape_sys_evaluater.py
@@ -88,13 +88,7 @@ class BinningMaskManager:
             assert all(c in df.columns for c in groupby_cols), [c for c in groupby_cols if c not in df.columns]
             assert len(groupby_cols), groupby_cols
 
-        required_cols = (
-            [
-                groupby_cols,
-            ]
-            if isinstance(groupby_cols, str)
-            else list(groupby_cols)
-        )
+        required_cols: List[str] = [groupby_cols] if isinstance(groupby_cols, str) else list(groupby_cols)
         __df = df[required_cols].copy(deep=True)
 
         for bin_col in self.ordered_binning_cols: