added doc string

app.py

@@ -14,6 +14,18 @@ classes = ('plane', 'car', 'bird', 'cat', 'deer',
            'dog', 'frog', 'horse', 'ship', 'truck')
 
 def inference(input_img, transparency = 0.5, target_layer_number = -1, num_top_classes = 5):
+    """This function take input as an image and generate Grad Cam image of it.
+
+    Args:
+        input_img (_type_): Input image provided by user.
+        transparency (float, optional): _description_. Defaults to 0.5.
+        target_layer_number (int, optional): Output of layer which will be given to Grad Cam. Defaults to -1.
+        num_top_classes (int, optional): To show number of classes to show in the output. Defaults to 5.
+
+    Returns:
+        top: Top Classes and Confidence level of the prediction
+        visualization: Grad Cam output
+    """
     transform = transforms.ToTensor()
     org_img = input_img
     input_img = transform(input_img)