diff --git a/mlptrain/configurations/configuration_set.py b/mlptrain/configurations/configuration_set.py
index 1ec46245..c256e864 100644
--- a/mlptrain/configurations/configuration_set.py
+++ b/mlptrain/configurations/configuration_set.py
@@ -434,7 +434,10 @@ def _coordinates(self) -> np.ndarray:
             (np.ndarray): Coordinates tensor (n, n_atoms, 3),
                           where n is len(self)
         """
-        return np.array([np.asarray(c.coordinates, dtype=float) for c in self], dtype=object)
+        return np.array(
+            [np.asarray(c.coordinates, dtype=float) for c in self],
+            dtype=object,
+        )
 
     @property
     def plumed_coordinates(self) -> Optional[np.ndarray]:
@@ -486,7 +489,8 @@ def _atomic_numbers(self) -> np.ndarray:
         """
 
         return np.array(
-            [[atom.atomic_number for atom in c.atoms] for c in self], dtype=object
+            [[atom.atomic_number for atom in c.atoms] for c in self],
+            dtype=object,
         )
 
     @property