diff --git a/vizro-core/src/vizro/_vizro.py b/vizro-core/src/vizro/_vizro.py
index 2588a462d..170e47aeb 100644
--- a/vizro-core/src/vizro/_vizro.py
+++ b/vizro-core/src/vizro/_vizro.py
@@ -51,11 +51,12 @@ def __init__(self, **kwargs):
             title="Vizro",
             use_pages=True,
         )
-        
+
         # Ensure external_stylesheets is a list and append the additional stylesheet
         external_stylesheets = self.dash.config.external_stylesheets
-        self.dash.config.external_stylesheets = external_stylesheets if isinstance(external_stylesheets, list) else [
-            external_stylesheets]
+        self.dash.config.external_stylesheets = (
+            external_stylesheets if isinstance(external_stylesheets, list) else [external_stylesheets]
+        )
         self.dash.config.external_stylesheets.append(dmc.styles.DATES)
 
         # When Vizro is used as a framework, we want to include the library and framework resources.