diff --git a/zesje/images.py b/zesje/images.py
index 05acb9eb2b6e4edfb3b53467dce4eeb3226ce880..469cf9d093e8d9870705264de6f420cae38d0b54 100644
--- a/zesje/images.py
+++ b/zesje/images.py
@@ -4,6 +4,7 @@ import numpy as np
 
 from operator import sub, add
 
+
 def guess_dpi(image_array):
     h, *_ = image_array.shape
     resolutions = np.array([1200, 600, 400, 300, 200, 150, 120, 100, 75, 60, 50, 40])
diff --git a/zesje/pregrader.py b/zesje/pregrader.py
index 440159681bf921fccb5fe30bad0632575f40e397..269c81be83c9f7b35f6c671a1a62ecfc2ddcdf3e 100644
--- a/zesje/pregrader.py
+++ b/zesje/pregrader.py
@@ -53,13 +53,13 @@ def box_is_filled(box, page_img, corner_keypoints, marker_margin=72/2.54, thresh
     page_img: np.array
         A numpy array of the image scan
     corner_keypoints: (float,float)
-        The x coordinate of the left markers and the y coordinate of the top markers, 
-        used as point of reference since scans can deviate from the original. 
+        The x coordinate of the left markers and the y coordinate of the top markers,
+        used as point of reference since scans can deviate from the original.
         (x,y) are both in pixels.
     marker_margin: float
         The margin between the corner markers and the edge of a page when generated.
     threshold: int
-        the threshold needed for a checkbox to be considered marked range is between 0 (fully black) 
+        the threshold needed for a checkbox to be considered marked range is between 0 (fully black)
         and 255 (absolutely white).
     cut_padding: float
         The extra padding when retrieving an area where the checkbox is in inches.
@@ -139,11 +139,3 @@ def box_is_filled(box, page_img, corner_keypoints, marker_margin=72/2.54, thresh
     if res_x < 0.333 * box_size_px or res_y < 0.333 * box_size_px:
         return True
     return np.average(res_rect) < threshold
-
-
-def box_is_filled(box, page_img, marker_position, marker_margin=72/2.54):
-    pass
-
-
-def _locate_checkbox():
-    pass