diff --git a/csst_proto/flip_image.py b/csst_proto/flip_image.py
index 94614620ac426a2d812c4dde4455c86ba192a1f6..d10254ccba585cea9a3feca6ad75d0a8a9c0b57b 100644
--- a/csst_proto/flip_image.py
+++ b/csst_proto/flip_image.py
@@ -1,24 +1,27 @@
 import numpy as np
-from astropy import table
 from . import PACKAGE_PATH
 
 
 # the main algorithm
 def flip_image(img: np.ndarray) -> np.ndarray:
-    """ flip an input image
+    """
+    Flip an input image.
 
     This function uses an awesome algorithm to flip an input image.
 
     Parameters
     ----------
-    img:
-        the input image
+    img : np.ndarray
+        The input image.
 
     Returns
     -------
-    img_flipped: np.ndarray
-        the flipped image
+    np.ndarray
+        The flipped image.
 
+    Examples
+    --------
+    >>> flip_image(np.array([1, 2], [3, 4]))
     """
     try:
         assert img.ndim == 2
@@ -30,7 +33,20 @@ def flip_image(img: np.ndarray) -> np.ndarray:
 
 # a demo on how to read test image
 def read_test_image():
-    """ read test image """
+    """
+    Read test image.
+
+    This function reads the test image associated with this package.
+
+    Returns
+    -------
+    np.ndarray
+        The test image.
+
+    Examples
+    --------
+    >>> test_image = read_test_image()
+    """
     fp_img = PACKAGE_PATH + "/data/test_image.txt"
     print("reading file {} ...".format(fp_img))
     return np.loadtxt(fp_img, dtype=int)
diff --git a/csst_proto/some_other_modules.py b/csst_proto/some_other_modules.py
index 3c73225d68c895e49383f3ff5eb65e93a11b1dbd..e9c24176e7c81a2d0b2a7705e63c6feaf516f880 100644
--- a/csst_proto/some_other_modules.py
+++ b/csst_proto/some_other_modules.py
@@ -1,3 +1,16 @@
 def a_demo_function(*args):
-    """ a demo function """
+    """
+    A demo function.
+
+    This function is a demo.
+
+    Parameters
+    ----------
+    *args : any
+        The argument list.
+
+    Examples
+    --------
+    >>> a_demo_function(None)
+    """
     return None