diff --git a/src/bob/io/base/__init__.py b/src/bob/io/base/__init__.py
index 5811450abf63b4d3418fe231c670defa55306049..6b0b20d8d7b2007b1843880d5282158d21f6085e 100644
--- a/src/bob/io/base/__init__.py
+++ b/src/bob/io/base/__init__.py
@@ -67,6 +67,7 @@ def open_file(filename) -> np.ndarray:
     ``filename`` : str
       The name of the file to open.
     """
+
     def check_gray(img):
         # Checking for gray scaled images
         if (