updated docstring

csst_proto/flip_image.py

@@ -4,7 +4,7 @@ from . import PACKAGE_PATH
 
 
 # the main algorithm
-def flip_image(img: np.ndarray):
+def flip_image(img: np.ndarray) -> np.ndarray:
     """ flip an input image
 
     This function uses an awesome algorithm to flip an input image.
@@ -16,14 +16,16 @@ def flip_image(img: np.ndarray):
 
     Returns
     -------
-    the flipped image
+    img_flipped: np.ndarray
+        the flipped image
 
     """
     try:
         assert img.ndim == 2
+        img_flipped = img[::-1, ::-1]
+        return img_flipped
     except AssertionError:
         raise AssertionError("The input image is {}D not 2D!".format(img.ndim))
-    return img[::-1, ::-1]
 
 
 # a demo on how to read test image

csst_proto/some_other_modules.py

+def some_arbitrary_functions():
+    """ an arbitrary function """
+    return

csst_proto/top_level_interface.py

 from .flip_image import flip_image, read_test_image
+from .some_other_modules import some_arbitrary_functions
 
 
-__all__ = ["flip_image", "read_test_image"]
+__all__ = ["flip_image", "read_test_image", "some_arbitrary_functions"]