diff --git a/mne_gui_addons/_core.py b/mne_gui_addons/_core.py
index babd65f..e38dcc2 100644
--- a/mne_gui_addons/_core.py
+++ b/mne_gui_addons/_core.py
@@ -127,7 +127,9 @@ def __init__(self, base_image=None, subject=None, subjects_dir=None, verbose=Non
             op.join(subjects_dir, subject) if subject and subjects_dir else None
         )
         if self._subject_dir is None and base_image is None:
-            raise ValueError('`subjects_dir` must be provided if no `base_image` is provided')
+            raise ValueError(
+                "`subjects_dir` must be provided if no `base_image` is provided"
+            )
         self._load_image_data(base_image=base_image)
 
         # GUI design
@@ -354,7 +356,7 @@ def _plot_images(self):
             rr = apply_trans(self._vox_ras_t, rr)
             self._head["rr"] = rr
             self._head["tris"] = tris
-       
+
         self._head_actor, _ = self._renderer.mesh(
             *self._head["rr"].T * 1000,
             triangles=self._head["tris"],