add example

app.py

@@ -47,8 +47,9 @@ def HILL(input_image, operation, message, key):
         return 'tmp/stego.png'
 
 iface = gr.Interface(HILL, 
-                    ["file", gr.inputs.Radio(["encode", "decode"]), "text", "text"], 
-                    "file", 
+                    ['file', gr.inputs.Radio(['encode', 'decode']), 'text', 'text'], 
+                    'file', 
+                    examples=[['tmp/8825.png', 'encode', 'This is a secret message', 'secret-key']],
                     title=title,
                     description=description)
 iface.launch()