Apply batched suggestions from code review

Co-authored-by: Christian Clauss <cclauss@me.com>

Author: cclauss

computer_vision/mean_threshold.py

@@ -6,7 +6,7 @@
 """
 
 
-def mean_threshold(image: Image) -> Image.Image:
+def mean_threshold(image: Image.Image) -> Image.Image:
     """
     image: is a grayscale PIL image object
     """

computer_vision/otsu_threshold.py

@@ -7,7 +7,7 @@
 """
 
 
-def otsu_threshold(image: Image) -> Image.Image:
+def otsu_threshold(image: Image.Image) -> Image.Image:
     """
     Applies Otsu's thresholding method to a grayscale image.
 

digital_image_processing/change_brightness.py

@@ -1,7 +1,7 @@
 from PIL import Image
 
 
-def change_brightness(img: Image, level: float) -> Image.Image:
+def change_brightness(img: Image.Image, level: float) -> Image.Image:
     """
     Change the brightness of a PIL Image to a given level.
 

digital_image_processing/change_contrast.py

@@ -11,7 +11,7 @@
 from PIL import Image
 
 
-def change_contrast(img: Image, level: int) -> Image.Image:
+def change_contrast(img: Image.Image, level: int) -> Image.Image:
     """
     Function to change contrast
     """