diff --git a/csst_proto/some_other_modules.py b/csst_proto/demo.py
similarity index 97%
rename from csst_proto/some_other_modules.py
rename to csst_proto/demo.py
index 1f1d2baf89cd4b0a11976dd10bd5565018e8be91..3d753e89e0a22a7bc5cac1565f314090a1144ada 100644
--- a/csst_proto/some_other_modules.py
+++ b/csst_proto/demo.py
@@ -13,7 +13,7 @@ def a_demo_function(*args):
     --------
     >>> a_demo_function(None)
     """
-    return None
+    return len(args)
 
 
 class ADemoClass:
diff --git a/csst_proto/top_level_interface.py b/csst_proto/top_level_interface.py
index ea4f113675f7adacc8927fc96e7e3892198da0c6..7e4531e2ff0221e1c89a2c439c3f301c3c284b7f 100644
--- a/csst_proto/top_level_interface.py
+++ b/csst_proto/top_level_interface.py
@@ -1,5 +1,5 @@
 from .flip_image import flip_image, read_test_image
-from .some_other_modules import a_demo_function, ADemoClass
+from .demo import a_demo_function, ADemoClass
 
 
 __all__ = ["flip_image", "read_test_image", "a_demo_function", "ADemoClass"]